To provide a propellant tank such as a fuel tank and an oxidant tank for a spacecraft, the propellant tank discharging propellant such as liquid hydrogen and liquid oxygen accumulated therein toward a rocket engine by pressurizing an inside thereof by operating gas. The propellant tank includes a tank body that accumulates therein the propellant in a liquid state, and a holding container that is provided inside the tank body and disposed with a predetermined gap from an inner wall of the tank body, so that the propellant in a liquid state can be held therein, when the inside of the tank body is in a microgravity state or a zero-gravity state.