A pumping loss calculation device for an internal combustion engine, which is capable of accurately calculating the pumping loss of the engine while reflecting thereon the pumping loss which varies with a change in opening timing of an exhaust valve. The pumping loss calculation device calculates a basic amount of a pumping loss torque based on intake and exhaust pressures, a pumping loss torque of the pumping loss torque of the engine, which varies with a change in the opening timing of the exhaust valve, as an exhaust gas sweep-out loss torque, based on the estimated in-cylinder gas amount and a detected exhaust phase, and the pumping loss torque based on the basic amount and the exhaust gas sweep-out loss torque.