The invention concerns an actuating device (1) for moving a mobile cover of a thrust reverser, comprising: an actuator (5) comprising a first element (10), such as a screw, and a second element (12), such as a nut, mounted mobile device relative to the first element (10) such that the rotation of the first element (10) results in a translational movement of the second element (12) relative to the first element (10), and a locking device (31) comprising a rotating part (34) linked in rotation with the first element (10), and a locking part (35) that is mobile relative to the rotating part (34) between a locked position in which the locking part (35) is engaged with the rotating part (34) to prevent the first element (10) from rotating and an unlocked position in which the locking part (35) is disengaged from the rotating part to allow the rotation of the first element (10), and an electromagnet (39) for moving the locking part (35) to the unlocked position.