beautiful is most pretty. Mostly pretty=beautiful.

Hello Beautiful is a degree higher and more general than pretty A beautiful girl would have more attributes than a pretty girl .

beautiful = 美丽/超级美， pretty = 稍微美一点/漂亮/可爱 there are lots of differences but both are considered good! haha 意思没相差太多不过还有点差别。 beautiful 还可以指抽象思维但 pretty 用来说肤浅的事物 比如说: the way that room was set up for the wedding was so beautiful the shirt she wore to school today was very pretty life is beautiful and so are you look at the pretty flowers outside the window that girl is pretty but not very sexy i can't believe how beautiful you look tonight having a pretty smile can help you make new friends, but having a beautiful smile can get you many modeling jobs

You can safely assume, for the most part, that beautiful ~= 美/美麗 pretty ~= 漂亮 with the slight differences that are similar to Chinese. Beautiful seems more formal and a level higher than pretty. I agree with Cherry's answer above. Consequently, one would probably use "beautiful" less often.