A socket for a fluid-transfer coupling device (5) that communicates a flow path in the socket with a flow path in a plug (70) since the socket (10) and the plug are connected to each other, includes a mount panel attachment (17) arranged in the vicinity of an entry (19) of the socket allowing the plug to be inserted, and attaching the socket to a mount panel (18) and a support (35) arranged in a different position from the entry and supporting the socket. Consequently, the socket can be stably supported on the mount panel even if the flow rate of fluid is large. It is preferable that at least one part of the socket is constructed in a spigot-and-socket manner.