A valve timing controller includes a housing which is biasedly assembled in such a manner that the housing is previously moved in a direction where a rotor knocks the housing. A camshaft rotatably extends through a through-hole provided in a sprocket and is engaged with a camshaft-inserting hole provided in the rotor. An inner diameter of the camshaft-inserting hole is lager than an inner diameter of the through-hole provided in the sprocket in order to prevent the camshaft-inserting hole from overlapping the through-hole.