Under industrial scenarios, high-speed motion is an important factor in increasing productivity. In this paper, a linear variable structured elastic actuator (LVSEA) is proposed for high-speed linear motion. The LVSEA consists of a geared motor, an electromagnetic clutch, a ball screw, compression springs, and a flange. The clutch is located between the geared motor and the ball screw. The clutch disconnects the geared motor from the ball screw. The compression springs are located between a housing and the flange of the ball screw. The spring stores elastic energy using the geared motor via the ball screw and the clutch. The stored elastic energy is released as kinetic energy by disconnecting the ball screw from the geared motor. On the load side, low inertia and low friction are achieved by disconnecting the ball screw from the geared motor, and high-speed movement is thereby realized. In the experiment, the velocity of a conventional ball screw system driven by the geared motor was 0.014 m/s. By contrast, the velocity of the LVSEA was 0.898 m/s. Therefore, the LVSEA could move faster than the conventional system. We verified repeating motions to reciprocate from position to position of the LVSEA and the conventional system. The average reciprocating time of the LVSEA was 4.76 s. By contrast, the average reciprocating time of the conventional system was 8.74 s. Therefore, the repeating motion of the LVSEA was faster than that of the conventional system.