Linear actuator comprising an electric motor (2) which through a transmission (3) drives a spindle unit, where the spindle unit comprises at least one spindle (4) with a spindle nut (5), where the spindle (4) is equipped with a bearing (8). In connection with the spindle unit there is an adjustment element (6), typically tubular. In order to retain the adjustment element (6) in a given position when the power supply for the electric motor (2) is interrupted, a brake (11) comprising a spring (15) and a cylindrical element (12) is provided. The cylindrical element (12) has a threaded pin (12a) on which a nut (13) is arranged, and where the spring (15) is positioned around the cylindrical element (12) between one side of the nut (12) and a stop (14) on the cylindrical element (12) such that the spring (15) presses the nut (13) with its other side against a contact surface (16). The brake power is thus generated by the nut rubbing against the contact surface with its one side. It is thus an alternative brake construction having a simple construction and where the spring only exerts a compressive force. The brake power can be adjusted to the spring power, and the friction between the nut and the contact surface and finally the thread pitch on the nut.