SOS Encounter: Route 1, Hau'oli City (Only in Sun & Moon)
Walk: Route 1 (5%), Hau'oli City (5%, Only in Sun & Moon)
Its base catch rate is 190 out of 255 (higher is easier); the catch rate calculator works out your odds with each ball. For the look, the best colour match is Ultra Ball or Level Ball.
Evolution: Pichu → Pikachu → Raichu (Thunder Stone).
Pichu in every game · Pokémon Sun, Moon, Ultra Sun & Ultra Moon interactive map (Alola)