Let me make it clear that you should never show up too early for the interview.
How early is Too Early? I say anything more than ten minutes is too early.
You want to show that you can be on time, but an hour early is way too early.
At an hour early, everyone is wondering who you are and why you are still sitting there.
Buzz is happening in the office, the receptionist gets nervous.
You are wasting time, which may be a Red Flag in itself to the hiring manager.
You are also not being respectful of your hiring manager's time.
Be respectful. Show up ten, fifteen minutes early MAX. Anything more looks like you have nothing better to do..