To provide a simply structured practical locking device for a crime prevention buzzer at a low cost which is easily switched between the time of use and the time of non-use of the crime prevention function.

The locking device 10 for the crime prevention buzzer to be installed on a double sliding door or the like comprises a receiving part 16 disposed on an inner side of an outer door body 14 in a manner that the double sliding operation of the inner and outer door bodies is not hindered, a stopping mechanism 20 fixed to a double sliding wall 18 of the inner door body 12 for stopping the double sliding movement of the inner and outer door bodies 12, 14 by a stopping member 26 protruding from and retreating to the side of a runway space S, which stopping member 26 engages with the receiving part 16 when protrudes, an alarm device 22 outputting an alarm according to contact or non-contact of elements (48, 50) of the inner and outer door bodies 12, 14. The alarm is generated and an opening operation is stopped upon the opening operation of the door or the like to prevent a crime. Further, the switch-over between use and non-use of crime prevention function is performed by protruding or retreating the stopping member from/to the side of the runway space with the whole device attached to the door or the like.