A pump-free water-cooling system is provided wherein external power supply is not involved; heat can be transported in any direction; and high reliability and low thermal resistance are ensured.The pump-free water-cooling system includes: a heat-exchange circulating solution container in which a heat-exchange circulating solution and vapor of the circulating solution are contained; a heat radiator provided on the outer wall of the container; a solution outlet for discharging from the container the heat-exchange circulating solution in the container; a gas-liquid two-phase fluid inlet for charging into the container gas-liquid two-phase fluid composed of the heat-exchange circulating solution at high temperature and vapor bubbles of the circulating solution; a first transportation route along which a sensible-heat-emitting heat exchanger is provided, the first transportation route linking with the solution outlet; a second transportation route along which heat exchange is carried out between heat-exchange circulating solution therein and the heat-exchange circulating solution in the container and the vapor of the heat-exchange circulating solution in the container; a third transportation route along which a heating heat exchanger is provided, the third transportation route linking with the gas-liquid two-phase fluid inlet; and a circulating-solution transporting route in which the first transportation route, the second transportation route, and the third transportation route are linked in that order.