Beautiful is used to refer to a woman or a child, who are attractive in a noticeable way. Pretty is used to refer to a woman or a girl, who have a nice, attractive face. Handsome is used to refer to a man or a boy, who are good-looking, attractive.
She was more beautiful than I had remembered. What a beautiful child! Julia Roberts is really beautiful.
pretty She looks pretty with that new haircut. They have a pretty little girl. Julia Roberts is really pretty.
He is tall, blond and handsome. They have a handsome young boy. George Clooney is really handsome.