A linear actuator. On a guide block that configures a guide mechanism, a pair of ball-circulating grooves is formed on the lower surface that faces a cylinder body and multiple balls are loaded in the ball-circulating grooves. Paired cover blocks are respectively mounted on the two ends of the guide block. Paired ball clips, which are formed as arms, are engaged with the cover blocks when the clips are inserted in the ball-circulating grooves and are holding the balls. Paired cover plates are respectively mounted on the end faces of the cover blocks, and arm-shaped cover clips are mounted so as to hold the cover plates. The cover plates, the cover blocks and the guide block are thereby integrally linked.