OBJECT: To provide a compact phase varying device for an automobile engine, adapted to vary the relative phase angle between the crankshaft of the engine and the camshaft of the device over a wider range than that of conventional device.MEANS FOR ACHIEVING THE OBJECT:The phase varying device has: a drive rotor driven by the crankshaft of the engine; a first control rotor rotatable relative to the drive rotor under the action of a torque means; and a phase angle varying mechanism operably coupled to the first control rotor in rotational motion relative to the first control rotor, the drive rotor and first control rotor rotatably supported by a camshaft of the phase varying apparatus, the phase varying device adapted to vary the phase angle of the camshaft relative to the crankshaft by varying the phase angle of the camshaft relative to the drive rotor. The phase angle varying mechanism is characterized by comprising: a first circular eccentric cam integrated with the first control rotor and having a center eccentrically offset from the rotational axis of the camshaft; a second circular eccentric cam integrated with the camshaft and having a center eccentrically offset from the rotational axis of the camshaft; a cam guide member for rotatably coupling the first circular eccentric cams with the second circular eccentric cam and for converting the eccentric rotational motion of the first circular eccentric cam into the eccentric rotational motion of the second circular eccentric cam.