An internal combustion engine torque estimation device that accurately estimates the torque of an internal combustion engine without being affected by engine speed changes. A reference signal, which is output at predetermined rotation angle intervals of a crankshaft for the engine, is acquired. In accordance with the reference signal, the amount of change in the rotation speed of the crankshaft is acquired as a rotational fluctuation. A filtering process is performed on the rotational fluctuation in synchronism with reference signal output timing to extract a frequency component synchronized with a combustion cycle of the engine. The torque of the engine is estimated in accordance with the extracted frequency component.