To solve a problem caused when a hydraulic actuator is used in a variable valve timing device.

In the variable valve timing device, rotation is transmitted through a planetary traction drive unit 10 to a portion between a camshaft 2 and a sprocket 1 rotated in synchronization with a crankshaft through a timing belt or the like. The planetary traction drive unit 10 includes a ring roller 5 rotated integrally with the sprocket 1, a sun roller 14 arranged inside the ring roller 5, and a planetary roller 11 rolling between the inner peripheral surface of the ring roller 5 and the outer peripheral surface of the sun roller 14. Furthermore, the planetary traction drive unit includes a carrier 12 rotatably and revolvingly supporting the planetary roller 11 and also rotated integrally with the camshaft 2. An electric motor 27 is provided for shifting the rotational phase of the carrier 12 with respect to the rotation of the ring roller 5 by rotatively driving the sun roller 14.