You can't, it needs a Thunder Stone.
thunder stone
Pikachu and Eevee both need a Thunder Stone to evolve.
Use a thunder stone
Pikachu will evolve into Raichu when given a thunder stone. If you mean Ash's Pikachu, then it very unlikely he will evolve his Pikachu, as Pikachu is the Pokemon Franchise's mascot.
Give Pikachu a Thunder stone and it will evolve into a Riachu. But in Pokemon Yellow, the Pikachu will not evolve. You can get thunder stones easy by mining them in Pokemon diamond and pearl but in soul silver and heart gold you need to buy them with athleet points at the athleet shop
a thunder stone can evolve a pikachu. pikachu won't evolve on it's own.
PIKACHU
thunder stone
eevee and pikachu.
In sunyshore city. I don't no where in sunyshore.
Pikachu and Eevee both need a Thunder Stone to evolve.
Use a thunder stone
Pikachu Can't Evolve Without The Thunder Stone.
pikachu
It is in Sunnyshore City near the lighthouse.
Pikachu will evolve into Raichu when given a thunder stone. If you mean Ash's Pikachu, then it very unlikely he will evolve his Pikachu, as Pikachu is the Pokemon Franchise's mascot.
Give Pikachu a Thunder stone and it will evolve into a Riachu. But in Pokemon Yellow, the Pikachu will not evolve. You can get thunder stones easy by mining them in Pokemon diamond and pearl but in soul silver and heart gold you need to buy them with athleet points at the athleet shop