In a valve actuation apparatus of a multi-cylinder engine employing a drive shaft rotatably arranged to extend over a plurality of cylinders, a drive cam attached to the drive shaft, and a motion transmitter provided for each of the cylinders for converting a rotary motion of the drive cam into an oscillating motion, a rockable-cam structural member is provided for each of the cylinders in a state where a shaft is inserted through inner peripheries of the rockable-cam structural members, for operating engine valves by the transmitted oscillating motion. A plain bearing is provided in at least one axial position between the axially-spaced rockable-cam structural members. An inner periphery of the plain bearing is in contact with an outer periphery of the shaft, whereas an outer periphery of the plain bearing is in contact with an inner periphery of a bearing portion mounted on the engine.