An internal combustion engine in which a fuel pressure is changed and a fuel injection quantity is controlled in accordance with an engine operating condition when a fuel injection is performed, the internal combustion engine comprising: a cylinder; a direct injection injector arranged so as to supply the fuel to the cylinder; a detection unit (38, 39) for detecting an operating condition of the internal combustion engine; and a control unit for controlling the fuel injection, including: two maps describing two factors of a fuel injection characteristic coefficient (Ka) and an invalid injection period (tb) with respect to the fuel pressure of the direct injection injector; a first calculating section for calculating a required fuel injection quantity necessary for injecting the fuel into the cylinder in accordance with an information from the detection unit (38, 39); a second calculating section for calculating a required fuel injection period in accordance with a following equation T=Ka x Q + tb and the required fuel injection quantity and the two factors of the fuel injection characteristic coefficient (Ka) and the invalid injection period (tb) with respect to the fuel pressure, both of which are obtained from the two maps; and a controlling section for controlling the fuel injection such that the fuel is injected for the required fuel injection period through the direct injection injector, characterized in that the required fuel injection quantity is decided in accordance with the operating condition of the internal combustion engine including at least an engine revolution speed, engine load and a fuel temperature. a cylinder; a direct injection injector arranged so as to supply the fuel to the cylinder; a detection unit (38, 39) for detecting an operating condition of the internal combustion engine; and a control unit for controlling the fuel injection, including: two maps describing two factors of a fuel injection characteristic coefficient (Ka) and an invalid injection period (tb) with respect to the fuel pressure of the direct injection injector; a first calculating section for calculating a required fuel injection quantity necessary for injecting the fuel into the cylinder in accordance with an information from the detection unit (38, 39); a second calculating section for calculating a required fuel injection period in accordance with a following equation T=Ka x Q + tb and the required fuel injection quantity and the two factors of the fuel injection characteristic coefficient (Ka) and the invalid injection period (tb) with respect to the fuel pressure, both of which are obtained from the two maps; and a controlling section for controlling the fuel injection such that the fuel is injected for the required fuel injection period through the direct injection injector, characterized in that the required fuel injection quantity is decided in accordance with the operating condition of the internal combustion engine including at least an engine revolution speed, engine load and a fuel temperature. two maps describing two factors of a fuel injection characteristic coefficient (Ka) and an invalid injection period (tb) with respect to the fuel pressure of the direct injection injector; a first calculating section for calculating a required fuel injection quantity necessary for injecting the fuel into the cylinder in accordance with an information from the detection unit (38, 39); a second calculating section for calculating a required fuel injection period in accordance with a following equation T=Ka x Q + tb and the required fuel injection quantity and the two factors of the fuel injection characteristic coefficient (Ka) and the invalid injection period (tb) with respect to the fuel pressure, both of which are obtained from the two maps; and a controlling section for controlling the fuel injection such that the fuel is injected for the required fuel injection period through the direct injection injector, characterized in that the required fuel injection quantity is decided in accordance with the operating condition of the internal combustion engine including at least an engine revolution speed, engine load and a fuel temperature.