An appendix to VKroz' answer:
The usual recommendation by HR experts is to dress in the same style and level of formality that the workers in the company or department that you apply for wear in their everyday business life.
A job interview is not a marriage or funeral. You must show your respect (and not dress sloppy), but you also must show that you know what you are applying for, so overdressing is a sign that you are ignorant and subtracts from your value. Outside of politics and top management, never dress better than your boss!
If you forgot or cannot ask the person that you will talk to (as VKroz recommends), you might look at the website of the company. They often have photographs of staff, and usually these photos are taken at work during working hours. Look how they dress. That is how you should dress to the job interview.
If there aren't any photos on the web, find comparable companies.
Don't be confused that the HR personnell will probably be wearing suits. Their role is to represent the company, and they usually dress impeccably. Don't imitate them, if you apply for a job as a programmer.
Wear something that fits and becomes you. Putting on an expensive suit from your tall friend that hangs on you like a sack will not help you. Better wear a pullover that compliments you and comment on it, if a suit was expected ("I know I'm not really dressed for the occasion, but ..." – be creative here, in the end you are hired for how well you handle obstacles, not your dress).