A linear actuator can obtain a roughly fixed load within a stroke range. The linear actuator comprises a fixed element, comprising a yoke and a magnet which is magnetized in the radial direction, and a moving element, comprising an electromagnetic coil and a bobbin which surrounds the magnet. A spring is provided for applying a force acting in opposition to the thrust direction acting on the moving element. A constant load stroke area is provided so that the characteristics of the opposite force of this spring balance the characteristics of the thrust force acting on the moving element. The constant load stroke area is an area where one end of the coil in the stroke direction is located in an outside position from one end of the magnet in the stroke direction, and the other end of the coil in the stroke direction is located in an inside position from both ends of the magnet in the stroke direction.