A liquid transfer connector according to the present disclosure is provided with a plug having a plug body in which a fluid channel is formed, a socket having a socket body in which a fluid channel communicating with the fluid channel is formed when the plug is connected, a plug body housing part provided in the socket body, that receives and houses a distal end of the plug body inserted therein at a time of connection, an O-ring provided in the plug body housing part, that seals an outer periphery of the plug body inserted in the socket body and a cleaning liquid supply hole that supplies a cleaning liquid into the plug body housing part at a position opposite to the distal end of the plug body with respect to the O-ring.