A negative pressure pump has: a casing; a pump portion; a drive-side clutch plate that rotates integrally with a drive shaft, is movable in an axial direction of the drive shaft, and is magnetic; a driven-side clutch plate that rotates integrally with a driven shaft and transmits the rotation of the drive shaft to the driven shaft as a result of the drive-side clutch plate becoming engaged with it; a coil spring that presses the drive-side clutch plate against the driven-side clutch plate; an electromagnet that produces a magnetic force counter to a pressing force and pulls the drive-side clutch plate away from the driven-side clutch plate; and a jutting wall portion that is disposed in the casing and receives the driven-side clutch plate on which the pressing force acts and a jutting wall portion that supports one end portion of the coil spring.