A first rotary member rotates with a crankshaft and has a first gear. A second rotary member rotates with a camshaft and has a second gear that is axially shifted from the first gear. A planetary rotary member has third and fourth gears, which are eccentrically meshed respectively with the first and second gears to perform a planetary motion. A biasing member is interposed between the planetary rotary member and a planetary carrier, which supports the planetary rotary member. The planetary rotary member is in contact with the biasing member at a contact portion having an axial center. The axial center is located on a radially inner side of a meshed portion between the second and fourth gears, which has a backlash larger than that of a meshed portion between the first and third gears.