[Object of the Invention] An object of the present invention is to provide a detachable connector between a face piece and a filter of a breathing apparatus comprising a bayonet connection mechanism for connecting a pair of members by pushing and twisting operation, wherein detaching of the filter from the face piece by accident or user error is effectively prevented.[Disclosure of the Invention] A detachable connector between a face piece and a filter of a breathing apparatus is provided with a bayonet connection mechanism for connecting a pair of members by pushing and twisting operation, and a lock mechanism for locking a connection between the pair of members by fitting a pin in a hole provided in an elastic member, wherein connecting motion of the bayonet connection mechanism synchronizes with locking motion of the lock mechanism so that connection of the filter and locking of the connection are carried out simultaneously when the filter is connected to the face piece, while unlocking motion of the lock mechanism precedes disconnecting motion of the bayonet connection mechanism so that unlocking of the connection precedes disconnection of the filter when the filter is disconnected from the face piece.