A connector including a plug and a socket. The socket includes: a socket body having an insertion hole formed therein; a columnar rotary valve inserted into the insertion hole; and a switching mechanism for switching an open state and a closed state. The rotary valve includes a pair of convex portions respectively in contact with both ends of the insertion hole to seal an outflow of a liquid; and a concave portion provided between the pair of convex portions and forming a cleaning space) in which a cleaning fluid is circulated between the concave portion and an inner peripheral surface of the insertion hole. The socket body includes a cleaning fluid inflow passage for guiding the cleaning fluid to the cleaning space and a cleaning fluid outflow passage through which the cleaning fluid flows out of the cleaning space.