A valve for a fuel tank, the valve being provided with: a valve main body (5) having a filling port (6) for filling a tank (100) with fuel gas (G) and an outlet (7) for outputting the fuel gas (G) within the tank (100); and a jet deflection piece (10) for jetting the fuel gas (G) filled from the filling port (6) at a predetermined angle relative to the axial direction of the tank (100). The jet deflection piece (10) is provided with: a fuel jetting unit (17) having a jet outlet (11) for jetting the fuel gas (G) into the tank (100); and a temperature measuring unit (13) on which a temperature sensor (20) for measuring the temperature of the fuel gas (G) to be filled into the tank (100) is disposed. As a consequence, it is possible to accurately measure and monitor the temperature of the fuel gas when filling the fuel tank with fuel.
