To provide a door locking device which ensures safety by allowing even a small child to open the door from the inside of a washing machine on his/her own.

This device is loaded with a heart-cam electromagnetic self-locking mechanism in which when a latch 20 on a washing machine door is in a locking position with a rotatable retainer body 3 caught in position and the latch 20 needs to become forcibly unlocked, the locking state can be released by bowing a movable stopper board 504 which holds the rotatable retainer body 3 in position, or in other words, through a forcible release mechanism in the rotatable retainer body 3 using the bowing function of a movable stopper board 5.