According to an aspect of the present invention, there is provided a fuel tank check valve including: a main tubular body attached on a fuel filler pipe; a valve element; a first tube that is disposed between the main tubular body and the fuel filler pipe and that has a first locking portion to engage with the fuel filler pipe; an annular seal member; and a second tube that is disposed to sandwich the annular seal member with the first tube and that has a second locking portion to engage with the main tubular body, wherein the fuel filler pipe is disposed on an inner circumferential surface of the first tube, wherein the first locking portion projects in an inside diameter direction, and wherein the first locking portion engages with an engagement hole in the fuel filler pipe from an outside.