A power control apparatus for a construction machine, comprising: an engine connected to a hydraulic pump to drive the hydraulic pump; and a controller for calculating an engine load ratio defined as a ratio of a load torque of the engine to an engine maximum torque calculated from an input engine target RPM, and for calculating an engine RPM command value according to the engine load ratio such that the engine is driven at the target RPM to output the calculated engine load ratio and engine RPM command value to the engine, the apparatus characterized in that the controller includes: an engine control unit for calculating the engine maximum torque from the engine target RPM, calculating the engine load torque from a fuel injection amount command value output to the engine, and calculating the engine load ratio from the calculated engine maximum torque and engine load torque to output the calculated engine maximum torque, engine load torque, and engine load ratio; and an equipment control unit for calculating the engine RPM command value from the engine load ratio output from the engine control unit to output the calculated engine RPM command value to the engine control unit, and wherein the engine control unit calculates the fuel injection amount command value according to the engine RPM command value transmitted from the equipment control unit to output the fuel injection amount command value to the engine. an engine connected to a hydraulic pump to drive the hydraulic pump; and a controller for calculating an engine load ratio defined as a ratio of a load torque of the engine to an engine maximum torque calculated from an input engine target RPM, and for calculating an engine RPM command value according to the engine load ratio such that the engine is driven at the target RPM to output the calculated engine load ratio and engine RPM command value to the engine, the apparatus characterized in that the controller includes: an engine control unit for calculating the engine maximum torque from the engine target RPM, calculating the engine load torque from a fuel injection amount command value output to the engine, and calculating the engine load ratio from the calculated engine maximum torque and engine load torque to output the calculated engine maximum torque, engine load torque, and engine load ratio; and an equipment control unit for calculating the engine RPM command value from the engine load ratio output from the engine control unit to output the calculated engine RPM command value to the engine control unit, and wherein the engine control unit calculates the fuel injection amount command value according to the engine RPM command value transmitted from the equipment control unit to output the fuel injection amount command value to the engine. an engine control unit for calculating the engine maximum torque from the engine target RPM, calculating the engine load torque from a fuel injection amount command value output to the engine, and calculating the engine load ratio from the calculated engine maximum torque and engine load torque to output the calculated engine maximum torque, engine load torque, and engine load ratio; and an equipment control unit for calculating the engine RPM command value from the engine load ratio output from the engine control unit to output the calculated engine RPM command value to the engine control unit, and wherein the engine control unit calculates the fuel injection amount command value according to the engine RPM command value transmitted from the equipment control unit to output the fuel injection amount command value to the engine.