A fluid coupling comprising a plug and a socket, the plug and the socket being coupled to each other so as to seal a fluid therebetween, each of the plug and the socket including: a valve; a spring that biases the valve so as to bring the valve into pressure contact with a valve seat formed on an inner circumferential surface of the plug or the socket; and a spring holder that positions and holds the spring, wherein each of the plug and the socket houses the valve, the spring, and the spring holder, when the plug is inserted into the socket, the valve of the plug and the valve of the socket abut against each other, and are retreated against biasing forces of the springs, and flow paths in the plug and the socket are connected to each other, wherein each of the valves includes: a largest diameter portion that abuts against the inner circumferential surface of the plug or the socket and positions the valve in an axial direction thereof; and inclined surfaces reduced in diameter into a conic shape from the largest diameter portion toward both sides in the axial direction, wherein one end of each of the springs is supported by the spring holder, and another end of each of the springs is housed in a spring mounting hole provided in the valve, and wherein each of the springs has an outer diameter sufficient for contacting an inside of the spring mounting hole, characterized in that each of the spring holders Includes: a base portion engaged with a step portion provided on an inner circumferential surface of the plug or the socket; raised walls raised from both edges of the base portion; and protrusions that protrude from the raised walls toward the valve concentrically with a center axis of the socket or the plug and support the spring. a valve; a spring that biases the valve so as to bring the valve into pressure contact with a valve seat formed on an inner circumferential surface of the plug or the socket; and a spring holder that positions and holds the spring, wherein each of the plug and the socket houses the valve, the spring, and the spring holder, when the plug is inserted into the socket, the valve of the plug and the valve of the socket abut against each other, and are retreated against biasing forces of the springs, and flow paths in the plug and the socket are connected to each other, wherein each of the valves includes: a largest diameter portion that abuts against the inner circumferential surface of the plug or the socket and positions the valve in an axial direction thereof; and inclined surfaces reduced in diameter into a conic shape from the largest diameter portion toward both sides in the axial direction, wherein one end of each of the springs is supported by the spring holder, and another end of each of the springs is housed in a spring mounting hole provided in the valve, and wherein each of the springs has an outer diameter sufficient for contacting an inside of the spring mounting hole, characterized in that each of the spring holders Includes: a base portion engaged with a step portion provided on an inner circumferential surface of the plug or the socket; raised walls raised from both edges of the base portion; and protrusions that protrude from the raised walls toward the valve concentrically with a center axis of the socket or the plug and support the spring. a largest diameter portion that abuts against the inner circumferential surface of the plug or the socket and positions the valve in an axial direction thereof; and inclined surfaces reduced in diameter into a conic shape from the largest diameter portion toward both sides in the axial direction, wherein one end of each of the springs is supported by the spring holder, and another end of each of the springs is housed in a spring mounting hole provided in the valve, and wherein each of the springs has an outer diameter sufficient for contacting an inside of the spring mounting hole, characterized in that each of the spring holders Includes: a base portion engaged with a step portion provided on an inner circumferential surface of the plug or the socket; raised walls raised from both edges of the base portion; and protrusions that protrude from the raised walls toward the valve concentrically with a center axis of the socket or the plug and support the spring. a base portion engaged with a step portion provided on an inner circumferential surface of the plug or the socket; raised walls raised from both edges of the base portion; and protrusions that protrude from the raised walls toward the valve concentrically with a center axis of the socket or the plug and support the spring.