A sealing member is composed of upper and lower holders which are molded members formed of rubber or resin. The upper holder has a stopper having a tubular shape with a flange inserted on its inner periphery. The lower holder has an inserted nut and outer threaded member on its inner and outer peripheries. In fixing a battery, after the outer threaded member of the lower holder is secured to a seat of a body frame by being screwed therein, the case is attached so that an expanded portion covers the lower holder, and then the upper holder is attached in a hole of the expanded portion. Subsequently, a bolt is presented through a battery holder, and is tightened by being screwed into the nut of the lower holder.