In a linear actuator (1), on the inside of a rectangular tubular movable element (3), a linear guide (14) that supports the movable element (3) so as to be linearly movable is positioned at a center of the movable element (3), and a position detecting mechanism (20) and load attaching member (13) that sandwich the linear guide are disposed linearly in a vertical direction. This arrangement enables a center of gravity of the movable element (3) to be matched with a center of the linear guide (14). A magnetic circuit is in a bilaterally symmetrical relationship with regard to the center of the movable element (3). Therefore, a center of a thrust force that acts upon the movable element (3) is matched with the center of the movable element (3). The center of the thrust force that acts upon the movable element (3), the center of gravity of the movable element (3), and the center of the linear guide (14) are positioned at the center of the movable element (3). Resistance to sliding in the movable element (3) can be reduced without unreasonable stress being placing on the linear guide (14). Therefore, a magnetically driven linear actuator that has highly precise positioning and that is durable can be realized.