A projection device includes at least one heat source and a heat dissipation module. The heat dissipation module is connected to the heat source and is configured to dissipate heat energy generated by the heat source. The heat dissipation module includes a tank, at least one radiator, at least one cold plate, a cooling fluid, and a connection pipe. The connection pipe connects the tank, the radiator, and the cold plate, so that the cooling fluid flows in the heat dissipation module. The tank includes a pressure sensing device configured to measure a liquid level of the cooling fluid in the tank. Also, a tank is provided. The projection device provided in the disclosure can learn the liquid level of the tank in real-time, and the design cost is low.