Control device of internal combustion engine, and internal combustion engine

Provided are a control device for an internal combustion engine, wherein the internal combustion engine is provided with a crank mechanism for converting a reciprocating motion of a piston into a rotating motion of a crankshaft, a cylinder accommodating the piston, and an intake valve capable of opening and closing an inlet for sucking gas into the cylinder, and the control device is provided with: a volumetric efficiency calculating unit for calculating a volumetric efficiency representing a suction efficiency when gas is sucked into the cylinder, on the basis of a cylinder capacity when the intake valve is closed; a gas suction amount calculating unit for calculating a gas suction amount sucked into the cylinder, by means of a predetermined formula, on the basis of the calculated volumetric efficiency; and a control unit for controlling the internal combustion engine on the basis of the calculated gas suction amount.