A valve device comprising: a body having a gas flow passage that in use establishes communication between an interior and an exterior of a gas tank in which high-pressure gas is stored; a joint that is attached to the body and that in use connects a pipeline to the gas flow passage; a check valve that restrains the gas inside the gas tank from flowing backward from the gas flow passage toward the joint and that is equipped with a valve seat having a valve hole and a valving element for opening/closing the valve hole ; a valve seat fixation member that fixes the valve seat to the body , that has a communication hole communicating with the valve hole , and that has an outer peripheral surface on which an external thread is provided; and a sealing member , wherein the body has an attachment hole that attaches the joint and the valve seat fixation member from an outside of the body in a sequence of the joint and the valve seat fixation member , and that has an inner peripheral surface in which an internal thread screwed to the external thread of the valve seat fixation member is provided, the sealing member , which maintains air tightness between the joint and the valve seat fixation member , is provided in a compressed state between the joint and the valve seat fixation member , an outer peripheral edge of the sealing member is located radially inward of a screwed region of the internal thread and the external thread characterised in that the joint has, at a tip portion of the joint that faces the valve seat fixation member , a sealing member accommodation portion that accommodates the sealing member , and the sealing member is compressed between the joint and the valve seat fixation member , with the tip portion abutting on an end surface of the valve seat fixation member that the tip portion faces. a body having a gas flow passage that in use establishes communication between an interior and an exterior of a gas tank in which high-pressure gas is stored; a joint that is attached to the body and that in use connects a pipeline to the gas flow passage; a check valve that restrains the gas inside the gas tank from flowing backward from the gas flow passage toward the joint and that is equipped with a valve seat having a valve hole and a valving element for opening/closing the valve hole ; a valve seat fixation member that fixes the valve seat to the body , that has a communication hole communicating with the valve hole , and that has an outer peripheral surface on which an external thread is provided; and a sealing member , wherein the body has an attachment hole that attaches the joint and the valve seat fixation member from an outside of the body in a sequence of the joint and the valve seat fixation member , and that has an inner peripheral surface in which an internal thread screwed to the external thread of the valve seat fixation member is provided, the sealing member , which maintains air tightness between the joint and the valve seat fixation member , is provided in a compressed state between the joint and the valve seat fixation member , an outer peripheral edge of the sealing member is located radially inward of a screwed region of the internal thread and the external thread characterised in that the joint has, at a tip portion of the joint that faces the valve seat fixation member , a sealing member accommodation portion that accommodates the sealing member , and the sealing member is compressed between the joint and the valve seat fixation member , with the tip portion abutting on an end surface of the valve seat fixation member that the tip portion faces. <EOS>