An idling position detecting switch for an internal-combustion engine, comprising a conductive tubular housing mounted on a throttle body of a throttle valve for regulating fuel-air mixture supply rate provided on an intake manifold for supplying a mixture to the combustion chamber of an internal-combustion engine, a push rod axially slidably supported in the housing and having one end projecting from one end of the housing so as to be in contact with a stopper connected to a valve shaft of the throttle valve, and the other end disposed within the housing and provided at the extremity thereof with a movable contact, a fixed contact disposed opposite to the movable contact within the housing, and a spring urging the push rod toward the stopper so that the movable contact is separated from the fixed contact and absorbing shocks applied to the push rod by the stopper of the throttle valve. The spring has one end firmly fixed to the push rod at a position near the movable contact and the other end firmly fixed to an inner surface of the housing. A detention mechanism is provided to prevent the turning motion of the spring within the housing due to a turning effect resulting from an axial sliding movement of the push rod.