Which episode does Orochimaru become good?

Naruto Shippuden Episode 341: Orochimaru’s Return. It is the episode in which Sasuke, technically, revives Orochimaru, and Orochimaru becomes nicer than before. He helps Sasuke to talk to the first 4 Hokage, and then Orochimaru helps the Allied Shinobi Forces by allowing the reanimated Hokages to join the war.

Does Orochimaru become good in Shippuden?

Orochimaru never changed from good to bad. He always did whatever he felt like to become immortal and/or more powerful. He wanted to kill Sarutobi,hence he invaded the Hidden Leaf Village. He joined Akatsuki, because he wanted to be more powerful and steal some of their techniques(especially Sharingan from Itachi).