A motor-driven compressor includes collars, which maintain the gap between a cover and an outer surface of a first housing member. Fasteners fasten the cover to the first housing member. Each collar is arranged to face a seating surface of the head of the corresponding fastener such that the cover is sandwiched between the collars and the seating surfaces. Each collar thus includes a facing portion, which faces the seating surface and receives a pressing force from the seating surface via the cover, and a transmitting portion, which transmits the pressing force received at the facing portion to a base member. Accordingly, the pressing force applied through the seating surface of the fastener is transmitted to the base member through the collar, so that the base member is pressed against the outer surface of the first housing member.