Abstract: A locking device for a door of a washing machine, a spin dryer or the like comprises a locking plate (10a) disposed on the machine and having the opening (11). A catch member (12) disposed on the door is insertable in the opening. In its locking position the catch member engages with an edge (14) bounding the opening in order to keep the door closed. An electrically operable blocking means (19) is provided to prevent the catch member from moving from the locking position as long as a rotatable drum or the like in the machine is operating. A releasing means (22,24,25) is provided to release the blocking means (19) as soon as the rotational movement has ceased. An electrical drive means (22) is provided to move the blocking means (19) to a blocking position against the action of a biasing means (21) which strives to move the blocking means to a lock releasing position.