PURPOSE: To absorb the torque fluctuation of a crankshaft or a camshaft so as to reduce a teeth striking sound.

CONSTITUTION: In a valve timing controller in which a ring gear 13 is moved in the shaft direction of a camshaft 2 so that the rotational phases of a timing pulley 6 and the camshaft 2 can be changed, a seal ring 18 is intervened between a timing pulley 6 and an outer gear 11, and also a compression coil spring 20 to press the outer gear 11 to the seal ring 18, is set. By this construction, the torque fluctuation of a crankshaft which is transmitted to the timing pulley 6, is absorbed accompanying the deformation of the seal ring 18. Therefore, the gearing noise of the ring gear 13 can be reduced. Further, the seal ring 18 is prevented from being changed in its elasticity by the heat of operating oil so that a table tooth striking sound reducing effect can be obtained.