A control apparatus of a construction machine includes a hydraulic pump driven by a prime mover, a hydraulic actuator, and a rotation speed detection device for detecting an actual rotation speed of the prime mover. The control apparatus includes a prime mover control device for controlling a rotation speed of the prime mover, and an input torque control device for adjusting an input torque for the hydraulic pump based on a deviation between the actual rotation speed detected by the rotation speed detection device and a control rotation speed set through an operation of the operating device, and the input torque control device executes control to decrease the input torque if the control rotation speed is greater than the actual rotation speed and the deviation calculated by subtracting the control rotation speed from the actual rotation speed is smaller than a predetermined negative value.