A fuel-tank fitting includes a cylinder-shaped fitting body including a connecting end to be connected with a pipe and a free end to be disposed freely inside a fuel tank, a flange disposed on an outer peripheral surface of the fitting body, and fastened to an opening periphery of an installation opening opened through the fuel tank, and a check valve disposed in the fitting body, openable only in a direction heading from the connecting end of the fitting body to the free end thereof, and closable for sealing a fuel. The fitting body further includes a first portion sealing the check valve, a second portion fastened to a portion of the flange, a third portion connecting the first and second portions, and a fragile portion fracturing more preferentially than the first and second portions and the flange fracture while securing a fuel-sealing ability inside the fuel tank.