Electrical units are effectively cooled, even if the longitudinal length of the cover member in which the electrical units to be cooled are accommodated is short, by easily guiding a flow of air during operation toward the electrical units. A second cover member which constitutes at least a part of a body cover together with a first cover member is positioned ahead of the first cover member which accommodates an electrical unit to be cooled. Inlets which let a flow of air during operation into the second cover member are disposed in the second cover member. An outlet for discharging a flow of air during operation out of the first cover member is provided in the first cover member.