Is your leave request formal or informal?
How many times have you asked him or her?
Did they give a reason?
Is there a contract or agreed procedure?
How big is the company?
Is there an HR dept?
Does your boss have a boss you can talk to?
Why are you still working there?
Remember - More details = better answers
Also: If you get a response it's polite to respond to it.
I recently had an employee say on Tuesday he was planning to take Thursday and Friday of that week off. He was part of our production team that was already short staffed, and we had three project deadlines that week. He had made no plans to have someone take his workload so him taking off puts the entire team in a tough spot. Should that leave have been approved?
I'm very pro taking time off, but it helps if we can plan a bit.
When I was working we had a saying, there's only TWO reasons why you can't take a vacation, either you haven't earned any, or you work for an a$$hole. I suspect that in your case it's the latter.
