PURPOSE: To improve accuracy in ignition timing by supplying air to a slide portion between a fixed bed plate and a movable one of a distributor for ignition to form air film, reduce friction and torque and improve responsive speed.

CONSTITUTION: When the rotation of an engine is increased, a relief valve 33 is operated to close an outlet 33c so that air from a connecting port 33a reaches a through hole, vent hole and annular groove to lift a movable bed plate 23 slightly from a fixed one 22 and reduce coefficient of friction between both plates. At the same time negative pressure is transmitted to a pressure responsive device 12 which produces torque to the movable bed plate 23 and is pivoted with the satisfactory responsive property to provide a proper ignition position. When the engine is shifted from high speed to low one, the reverse torque acts on the movable bed plate 23 which is pivoted without hysteresis and returned to a proper ignition position in low speed rotation. Thus, accuracy in the ignition timing can be improved.