A water electrolysis system includes a water electrolysis device; a water circulation circuit section including a water circulation pump; an antifreeze circulation circuit section including an antifreeze circulation pump; and a heat exchanger configured to perform heat exchange between the water circulation circuit section and the antifreeze circulation circuit section. Before water electrolysis is started by the water electrolysis device, a control device of the water electrolysis system circulates water by driving the water circulation pump and sets the antifreeze circulation pump to an operationally stopped state.