A linear actuator may include a fixed body having a coil wound around in a ring-shaped manner and a movable body. The movable body may include a first movable body side yoke which is disposed on the inner side of the coil and a pair of magnets which is laminated on both sides in an axial direction of the first movable body side yoke such that the same polarities of the magnets face the first movable body side yoke. The movable body may be driven in the axial direction. The linear actuator may be applied to a valve device and a pump device.