A linear actuator capable of realizing low dusting and low noise and having a large bearable load in axial direction, wherein a plurality of spacers 30...having spherical recessed parts corresponding to the curved surfaces of balls 28... at both ends thereof are installed between the balls 28...at a guide part and connected in series to a flexible band-like member 31, and a plurality of spacers 35 having spherical recessed parts corresponding to the curved surfaces of balls at both ends thereof and separated from each other are installed between the balls 33 for the screw shaft of a screw part, whereby, since a retainer 27 and the spacers 35 are selected according to the shapes of the guide part and the screw part, an unnecessary contact can be prevented from occurring between the balls and between the balls and a circulation passage around the balls to realize the low dusting and low noise.