A drive rotation member is driven by a crankshaft of the engine, and a driven rotation member is rotatable relative to the drive rotation member and secured to a cam shaft of the engine. An electric motor is arranged to rotate together with the drive rotation member and produces a dynamic power when fed with an electric current through brushes. A hollow control shaft is rotatable relative to the drive rotation member and forces the driven rotation member to rotate relative to the drive rotation member when rotated by the power of the electric motor. A bearing device is arranged between the driven rotation member and the hollow control shaft for smoothing a relative rotation therebetween. The bearing device includes a plurality of rollers. A lubrication oil feeding structure is provided for causing the rollers of the bearing device to be submerged in a lubrication oil at least when the engine is in operation.