PURPOSE: To enhance reliability of electric conduction by deviating an uppermost one of a plurality of button type batteries in the horizontal direction with respect to the other batteries in lower stages so as to prevent short-circuiting of the batteries due to a power source terminal and realize solder fixing of the power source terminal.

CONSTITUTION: Batteries 102, 104 are contained in a recess 26a of an inner case 26. The batteries 102, 104 are such constituted as to be deviated by a little of a radium of the battery in the horizontal direction. The battery 104 is supported at the outer periphery by an upper stage battery holding cylinder 26c. A plus terminal 22 is projected upward of the case 26 from a slit 26d formed between a lower stage battery holding cylinder 26b and the cylinder 26c so as to be brought into contact with the side surface of the battery 104. The terminal 22 is soldered at the base end 22a thereof a circuit board 18. Meanwhile, a minus terminal 20 is fixed to the circuit substrate 18, to be brought into contact with a negative electrode of the battery 102 at the lower stage via the slit of an insulating sheet 24. Consequently, it is possible to provide high reliability of electric conduction for the terminal 22 at its one end without any possibility of contact with the battery 102.