I'm finishing from my current job, and would like to ask for a reference. Whom shall I ask a reference from: from my supervisor, or from my manager?
Whom shall I ask a reference from: from my supervisor, or from my manager?
You could ask for reference to either of them. In fact, coworkers can also be used as references in some cases. Thus, it would be up to you to decide whom you want to ask.
You could always ask both if they would be willing to be your reference, and decide upon that (if only one of them agrees, then use that. If both agree, and your application only asks for one reference, chose either of those).
In practical terms one thing is asking for someone to be your reference and other is they actually agreeing to be your reference. In theory you should prefer to ask the one that you were closer to, and whom you had better relationship with.