PURPOSE: To enhance the flow-rate controllability to a great extent, by disposing a slider such that the slider comes to a completely closed position at the rotational position of an armature at which current is supplied only to a valve closing coil for the armature.

CONSTITUTION: An idling-speed control valve controls the engine speed at the time of idling operation by controlling the quantity of intake air passed through a by-pass passage. In respect of the relative angular position of a slider 4 and an armature 10, the slider 4 is fixed to a hollow shaft such that the slider 4 comes to a completely closed position at the rotational position of the armature 10 corresponding to the duty ratio 0% when current is supplied only to a valve closing coil. Thus, since the rotatable angular range of the slider 4 can be controlled in the range of 0% to 100% of the duty ratio, it is enabled to enhance the flow-rate controllability.