Variable valve actuation apparatus of internal combustion engine

In a variable valve actuation apparatus with a speed reducer between a timing sprocket and a camshaft for changing a phase of the camshaft relative to the sprocket, while reducing normal-rotation/reverse-rotation of an electric motor, the speed reducer includes an eccentric rotation member connected to an output shaft of the motor, an annular member connected to the sprocket, a plurality of rollers installed between an inner toothed portion of the annular member and an outer peripheral surface of the eccentric rotation member, and a cage connected to the camshaft for circumferentially partitioning the respective rollers, while permitting a radial displacement of each roller. Depending on a dimension of a clearance space between the eccentric rotation member and the annular member, a suitable one of a plurality of roller sets, each having a different outside diameter, is selected, and then the selected rollers are installed.