To perform the drawing operation of a battery without a failure for a long period.

A battery stand 5 on which the battery 3 is mounted is arranged to be movable forward (a) and backward (b) in a battery storage space 2 formed in the front part of a body 1. A protruded portion 18 is provided on a carriage 10 movable forward (a) and backward (b) along a pair of straddle leg extending frontward from the body 1. A rocking lever 30 heavier at its front end side is rockingly supported on the lower face of the battery stand 5. The carriage 10 is moved backward (b) to the lower part of the battery stand 5 to cancel the engaging condition of a rear end protruded portion 44 of the rocking lever 30 with a locking mechanism 19 provided on the body 1, whereby a hooking beam 30c of the rocking lever 30 is moved downward (c) with its dead weight to engage with the protruded portion 18 and the carriage 10 is moved forward (a) to draw the battery stand 5 from the battery storage space 2.