To provide an engine speed control method and device thereof capable of suppressing excessive rise and fall of the actual idling engine speed.

An idle-up corrective quantity QELS for correcting an idling engine speed control air quantity QISC used for controlling the engine speed at the time of idle running of an engine, is determined as the idle-up corrective quantity QELS correlated to radiator-fan driving duty (loaded amount) determined by a water temperature-cooling sensor, the car speed, etc. The idle-up corrective quantity is considered to be added to the idling engine speed control air quantity QISC, and thus the engine speed Ne at the time of idle running is controlled.