PURPOSE: To make it possible to easily lock a connector socket of a board attachment type which has become unable to lock by making the connector socket and a lock member to be freely attached to or detached from each other via a mating portion of the lock member.

CONSTITUTION: When a connector socket 1 is inserted into an opening 6a of a lock member 6 attached to a machine wall 3 and turned, the socket 1 is connected to the member 6 by means of a flange portion and a shaft cylinder portion 62 of the member 6. The member 6 is provided with a mating portion 66 so that the member 6 is freely detachably attached to a plug 4 via a mating portion 50 of the plug 4. With this constitution, the connector socket of a board attachment type which has become unable to lock can be easily locked.