To provide an attitude control device of a car carrier ship that can efficiently and economically perform an attitude control using freshwater from various freshwater tanks arranged inside the car carrier ship.

In addition to a bow trim adjustment tank 2, an aft central trim adjustment tank 3, an aft starboard trim adjustment tank 4, an aft port trim adjustment tank 5, a starboard heel adjustment tank 6 and a port heel adjustment tank 7, a port fire-extinguishing water tank 12 and a starboard fire-extinguishing water tank 13 are arranged. Freshwater stored in these port fire-extinguishing water tank and starboard fire-extinguishing water tank is transferred into the bow trim adjustment tank, the aft central trim adjustment tank, the aft starboard trim adjustment tank and the aft port trim adjustment tank and/or the starboard heel adjustment tank and the port heel adjustment tank, using a control pump 1, so that trim adjustment and heel adjustment are possible.