Well, you can use either one. But when talking about a man, you might rather say "handsome" instead of 'beautiful', as 'beautiful' is seen as more feminine. 

I agree that "beautiful" is a feminine word and "Handsome" is a masculine word, but I think "beautiful" is a bit more universal. For example, if we want to use either of these two in the case of a baby, then the priority goes to "Beautiful" irrespective of the gender. A "beautiful baby", but I have not listened people saying a "handsome baby" even if it's a baby boy!

"handsome" is used for male, "beautiful" is used for female.