To provide a method and a device for welding a stud with which even in the case of being an aluminum-base stud, desired welded shape and welded strength can surely be obtained.

For the purpose of welding the aluminum-base stud 11 onto an aluminum-base main material 14, electric current is divided into a plurality of steps (II, III, IV) and increased in order during generating period of a main arc. The tip of the melted stud comes into pressure contact with the melted main material within 5 mm second after the current of the main arc is interrupted.