This invention relates to a seawater battery-driven water vehicle for sailing in the ocean, including a main body, a flow channel, a seawater battery and a power system. The flow channel is disposed in the main body and includes an inlet, an outlet and a wall. The seawater battery is installed inside the flow channel, and includes the seawater that flows into the flow channel and a cathode and an anode that are connected with the wall respectively and separated from each other while contacted with the seawater. The power system is equipped on the main body and is electrically connected with the seawater battery and contacted with the ocean outside the main body. In this invention, accordingly, an electrochemical reaction respectively with the anode and the cathode in the flow channel is performed in the seawater to generate electric power, and the power system is driven by the electric power to push the main body to move in the ocean, so as to have a stable supply of electricity without reducing the carrying load of vehicle in water.