A linear actuator has inner yokes, outer yokes forming gaps between themselves and the inner yokes, and a movable body provided with planar magnets in the gaps. Eight pieces each of the inner yokes and the outer yokes are arranged at equal angular intervals in a circumferential direction with planar faces of each of the inner yokes and the of the outer yokes being opposed to each other. The movable body has magnet retaining portions having a substantially triangular shape and placed between adjacent inner yokes and between adjacent outer yokes. A linear actuator having high magnetism usability can be structured using magnetic parts suitable for mass production.