The present invention is directed to a power supply apparatus in which a battery and a circuit wiring board or boards are electrically connected by using lead terminals. The lead terminal (3) is adapted so that thickness of a welding portion (3a) is caused to be thinner than the thickness of a conductive portion (3b). Thus, current for welding flows to much degree in a thickness direction so that electric resistance of the welding portion becomes large, and heat based on the electric resistance also becomes large. From this fact, welding nugget (63) can be enlarged. As the result of the fact that large welding nugget is formed, the lead terminals are welded to terminal portions (37a) of the battery (2) with high reliability.