FUELING PORTION STRUCTURE OF FUEL TANK

To provide a fueling portion structure of a fuel tank that can reliably close a fueling port, and at which pulling-out of a fueling gun from the fueling port is made easy. A center of a rotation shaft (22) and a contact position when valve is closed (RP-1), that a spring (36) for the flapper valve contacts when a flapper valve (20) is at a closed-valve position (TP), are connected, and a reference segment when the valve is closed (RS-1) is assumed. The center of the rotation shaft (22) and a contact position when the valve is open (RP-2), at a time when the flapper valve (20) is at open-valve position HP, are connected, and a reference segment when the valve is closed (RS-2) is assumed. A spring shaft 42 (mounting portion 36B) is provided further toward the contact position when valve is closed (RP-1) side than a bisector (BS) of an angle formed by the reference segment when valve is closed (RS-1) and the reference segment when valve is open (RS-2).