PURPOSE: To suppress instantaneous reduction in idle rotating speed just after applying a load by setting, when the load is applied at the time of idle rotation of an internal combustion engine, the basic control amount of an actuator so as to control the intake pressure along an equal air quantity line according to a detected intake pressure and a determined target intake pressure.

CONSTITUTION: An idle rotating speed control unit controls a required actuator B by a means C according to the engine rotating speed detected by a means A. In this case, whether an internal combustion engine is in idle rotating state or not is detected by Q means D, whether a load is applied to the internal engine is also detected by a means E, and the intake pressure of the internal combustion engine is detected by a means F. In the means C, a target intake pressure is set by a means G from an equal air quantity line according to the engine rotating speed detection result. Thereafter, the basic control amount of the actuator is set from the detection result of each means D-F by a means H so as to control the intake pressure along the equal air quantity line according to the intake pressure detection result and the target intake pressure setting result, when the load is applied at the time of idle state.