To prevent erronious permission of a semi-fitting state caused by contamination of foreign matters and correctly detect a fitting state by installing a shielding plate in a lock arm for mutually locking connectors in a fixing state and installing a compressible and deformable spring part in a connection detecting contact.

When male, female connectors 33, 34 start fitting, a locking projection 54 installed in a lock arm 53 of the male connector 33 comes in contact with an inner wall 64 of a housing 51 to be energized, and the male connector 33 is inserted into the female connector 34 in a state that a shutter 55 blocks a fitting opening 45a of the locking projection 54. A tongue-like part 62c of a male terminal 62 comes in contact with the shutter 55, a spring part 62b is compressed and deformed, connection detecting female, male terminals 48, 62 are kept in a non-contact state, and when fitting is further advanced, the locking projection 54 is fit to a locking hole 58, the lock arm 53 is returned upward, the shutter 55 opens the opening 45a, and the tongue-like part 62c slides by repulsion force of the spring part 62b of the male terminal 62, and surely comes in contact with the female terminal 48.