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.