To provide a linear actuator in which backlash between a guide rail and a guide block is canceled and high positional accuracy of a movable body can be obtained and which can be made compact and inexpensive because of its simple configuration.

Inclined surfaces 37a and 38a of left and right split blocks 37 and 38 are made to abut on left and right inclined surfaces 6c and 6d of a guide rail 6. At least one or both of surfaces 37b and 38b facing a movable body side of the split blocks 37 and 38 are made to abut on an end face 6b of the guide rail 6, and thus the split blocks 37 and 38 are combined to the guide rail 6. Gaps between sliding surfaces 6b, 6c and 6d of the guide rail 6 and sliding surfaces 37b, 38b, 37a and 38a of the split blocks 37 and 38 are adjusted by adjusting the gap between the right and left split blocks 37 and 38. The respective split blocks 37 and 38 are fixed to the movable body 5 by using screw type fixing tools 40 and 41.