PURPOSE: To ensure the stability in engine rotation and to prevent a a nasty smell at the same time during idling of an engine, in which the engine revolutions during idling is increased if an air conditioner is working, by supplying an evaporating fuel when the engine is idling and moreover the air conditioner is working.

CONSTITUTION: This controller for engine idling revolutions is provided with an air conditioner working detecting means C1, which is used to detect whether or not an air conditioner is working, an idling detecting means C2, which is used to detect the idling state of the engine, and a first idling revolutions increasing means C3, which is used to increase the idling revolutions compared with the case in which the air conditioner is not working (C6), based on the outputs from both detecting means C1, C2, when the air conditioner is working and moreover the idling of the engine is detected. In addition, this controller is provided with an evaporating fuel supplying means C5, which is used to supply an evaporating fuel, based on the outputs from both detecting means C1, C2, when the air conditioner is working and moreover the idling of the engine is detected.