A three-port fluid selector valve is formed to have a large flow coefficient while making a structure of the valve compact. This three-port fluid selector valve allows fluid which has flowed from an inlet port 41 into a valve chamber 12 in a valve casing 1 to flow out of two outlet ports 42 and 43. Valve seats 13 and 31 communicating with the respective outlet ports are provided to opposite walls of the valve chamber 12 facing each other and a poppet-type valve body 5 for being selectively seated on the valve seats to connect the inlet port to one of the outlet ports and to close the other of the outlet ports is disposed in the valve chamber. The valve seats are formed in recessed shapes in the valve chamber 12 and provided to inner bottom portions of valve seat holes 17 and 18 having depths in which at least a half of a thickness of the valve body 5 at a periphery of the valve body 5 is embedded and suppresses reduction of the flow coefficient.