They're synonyms, but when translating them literally, one means "looks good" and the second one means "pretty".
好看 = good/nice looking/to describe the movie/book content is very good.
漂亮 = pretty/beautiful
这部电影非常漂亮。✖️
这本书非常好看。✔️(good content)
这本书非常漂亮。✔️(nice cover design)
她非常好看。✔️
她非常漂亮。✔️
这个设计很好看。✔️
这个设计很漂亮。✔️
（事情）干得好看！✖️
（事情）干得漂亮！✔️