A phase changing device for automobile engine, the device comprising curved first guide grooves formed in the control rotor, each groove skewed with respect to a circumference of a circle centered at the rotational axis; oblique guide grooves each groove formed in the middle rotor and extending at an angle with respect to a radius crossing the groove; second guide grooves formed in the drive rotor and skewed with respect to the circumference of a circle centered at the rotational axis, block sections each extending along, and movable in, the respective first guide; first slide members each protruding from the respective block section for engagement with, and for movement in, the respective skewed guide groove; and phase varying members each having a second slide member that extends through an escape groove formed in the middle rotor and engages the respective second guide groove to move in the second guide groove.