A drive-side rotor is rotated synchronously with a crankshaft. A driven-side rotor is rotated integrally with a camshaft. An internal gear section is formed at the driven-side rotor. An Oldham coupling includes: a driven Oldham flange that is formed at the drive-side rotor; a drive Oldham flange that is formed at the planetary rotor; and an Oldham intermediate that is configured to synchronize rotation of the driven Oldham flange and rotation of the drive Oldham flange while permitting eccentricity between the driven Oldham flange and the drive Oldham flange. There is satisfied a relationship of θ2