A one-way valve having a conduit for allowing liquid to flow therein, a valve element provided in the conduit, a hole portion provided in the conduit on the upstream side of the valve element and configured to be brought into a closed state by being closed by the valve element, and a spring that urges the valve element in the direction to close the hole portion, in which the peripheral surface of the valve element is formed with a first surface and a second surface intersecting the direction of movement of the valve element and generating a component force in the direction to close the hole portion when an urging force of the spring is applied, the first surface and the second surface are formed so as to increase the component force in the direction to close the hole portion as the valve element approaches the hole.