Negative pressure control apparatus and method therefor in an internal combustion engine

An apparatus and method for controlling a negative pressure in an internal combustion engine (10) equipped with a brake booster (18) that uses a negative pressure produced on a downstream side of a throttle valve (36) provided in an intake passage (34) of the engine, as a power source for amplifying the pedal pressing force. A controller (12) of the apparatus or method determines whether a negative pressure applied to the brake booster has reached a predetermined level when the internal combustion engine is started, and, if the negative pressure has not reached the predetermined level, increases an operating speed of the engine to a predetermined high speed and then keeps the throttle valve in a small opening state in which an opening amount of the throttle valve is smaller than that established when the internal combustion engine is in a fast idle state, during a period of time in which the engine proceeds to a steady-state operating mode.