Provided is a fluid transfer connector plug that allows for easy engagement of keys with key grooves. The fluid transfer connector plug includes: a plug body having a proximal end and a distal end, the proximal end allowing a hose to be fixed thereto, the distal end being removably connected to a socket, the plug body including a fluid channel communicating with the hose; a key plate on an outer periphery of the plug body, the key plate being rotatable relative to the plug body; and two or more keys on the key plate. The plug further includes a main key having a larger circumferential width than that of each of the other keys.