I am serving my notice period as I accepted an offer from other company. Now I have received a call from another company which is bigger than the other for interview. They asked me why I was in notice. Is it bad to hide to hide that i already have an offer from other company? By saying I have, will that make me to loose that interview?
First of all, let me say this:
You should not have disclosed that you're on notice period.
The only thing they can ask you or they need to know is: When (How soon) can you join? You can then, tell them the date you'll be okay to join. End of topic.
Now, coming to the point, when you have already disclosed you're on notice period,
Is it bad to hide to hide that i already have an offer from other company? By saying I have, will that make me to loose that interview?
Yes, it is bad, and does not need hiding. There's nothing to hide about a standing offer. You don't need to disclose any details about the offers, but mentioning you already have offers does not hurt.
This will serve you good, because the new company will know that you already have a standing offer, and
- If by allowing you to interview there is a possibility of legal issues, then they will not go ahead.
- Otherwise, if they do not see any issue in going ahead and making an offer, they will know about the other offer and based on the requirement, your scope for negotiation is bettered.
That said, to mention whether you "should" accept a new offer, if you get one after the interview - this really depends. As mentioned in the comments,
- it may burn some bridges at the first company, if you chose to accept the new offer
- or you may feel demotivated after joining at the first offer, if you chose to refuse the new offer
both has it's ups and downs. It's your call at the end of the day, how you want to play.
To frame-challenge your question a bit, it is important to emphasize this part of your question's text:
I am serving my notice period as I accepted an offer from other company.
You're stating that you've already accepted an offer from another company. Generally, this is viewed as having entered into a contract with that employer. While, of course, no one is going to force you to work for that employer, there is still significance in the act of making that commitment. Recruiters and hiring managers generally expect employees and candidates to respect their commitments. Doing so is considered a good sign in terms of your value as an employee.
That said, accepting an offer and then rejecting it because you got a better offer somewhere else is looked upon very poorly. While it's true that your potential future employers may never know that you did this, at least some of them will likely know (including, obviously, the company you're potentially stepping away from now). The significance of this rejection cannot be understated in some circles - in my own community, in my line of work, it's pretty common practice for third party recruiters, internal recruiters, and hiring managers to literally blacklist people who walk away from accepted offers like this, and not consider them for future positions.
Of course, there are no hard and fast rules, and some recruiters or hiring managers may not care about this, especially if they're in a very difficult employment market, or one where turnover isn't particularly expensive (for instance, unskilled entry level staff that don't have a big recruiting or onboarding cost). The real question is, do you know which situation you're in? Is it a gamble you're willing to take?
If you want to work for this new employer so badly that you're willing to risk that, then go ahead and follow up with the interview opportunity. It sounds like they've already learned you're on a notice period, and they've asked for an explanation (which is what your question is actually asking about):
They asked me why I was in notice. Is it bad to hide to hide that i already have an offer from other company?
If they haven't explicitly asked if you've accepted an offer elsewhere, and you haven't already disclosed that, it's probably not smart to specifically state that you've already accepted an offer (whether or not you're ethically comfortable with withholding that info is of course a question you have to ask yourself). Employers do expect that you'll be interviewing elsewhere and you may have other offers, so it's fair game to mention that generically, along the lines of stating that you "have other opportunities." That may even work in your favor, in the sense that it'll put the pressure on the new employer to act quickly if they want to make you a better offer.
As a final thought, there are plenty of questions on The Workplace asking about how to deal with very short tenures at employers, since "job hopping" is frowned upon. Consider that having accepted an offer, and then rejecting it to go for a better offer, is basically job hopping to the extreme - your tenure at the accepted offer was zero days!