A valve gear for an engine, comprising: a plurality of camshaft support portions provided in a cylinder head in a state in which the plurality of camshaft support portions are arranged in an axial direction of a crankshaft; a camshaft rotatably supported by the plurality of camshaft support portions, and including a cam configured to drive one of an intake valve and an exhaust valve; a rocker housing unit formed separately from the cam shaft support portions, and mounted on the cylinder head to be located between the camshaft support portions; a rocker shaft, two ends of which are supported by the rocker housing unit; a first rocker arm swingably supported by the rocker shaft; a second rocker arm swingably supported by the rocker shaft and selectively connected to the first rocker arm by a switch pin (65 - 67) movable in an axial direction of the rocker shaft; a first piston configured to move the switch pin to one side in the axial direction; a second piston configured to move the switch pin to the other side in the axial direction; and hydraulic supply portions (42, 47) configured to supply an oil pressure to the first piston and the second piston, characterized in that one piston, which is one of the first piston and the second piston, is provided in one rocker arm, which is one of the first rocker arm and the second rocker arm, the other piston is provided in the rocker housing unit located on a side opposite to the one piston in the axial direction across the other rocker arm, the hydraulic supply portion configured to supply the oil pressure to the one piston includes a first oil passage formed in the one rocker arm, the rocker shaft, and the rocker housing unit which supports one end of the rocker shaft, and the hydraulic supply portion configured to supply the oil pressure to the other piston includes a second oil passage formed in the rocker housing unit. a plurality of camshaft support portions provided in a cylinder head in a state in which the plurality of camshaft support portions are arranged in an axial direction of a crankshaft; a camshaft rotatably supported by the plurality of camshaft support portions, and including a cam configured to drive one of an intake valve and an exhaust valve; a rocker housing unit formed separately from the cam shaft support portions, and mounted on the cylinder head to be located between the camshaft support portions; a rocker shaft, two ends of which are supported by the rocker housing unit; a first rocker arm swingably supported by the rocker shaft; a second rocker arm swingably supported by the rocker shaft and selectively connected to the first rocker arm by a switch pin (65 - 67) movable in an axial direction of the rocker shaft; a first piston configured to move the switch pin to one side in the axial direction; a second piston configured to move the switch pin to the other side in the axial direction; and hydraulic supply portions (42, 47) configured to supply an oil pressure to the first piston and the second piston, characterized in that one piston, which is one of the first piston and the second piston, is provided in one rocker arm, which is one of the first rocker arm and the second rocker arm, the other piston is provided in the rocker housing unit located on a side opposite to the one piston in the axial direction across the other rocker arm, the hydraulic supply portion configured to supply the oil pressure to the one piston includes a first oil passage formed in the one rocker arm, the rocker shaft, and the rocker housing unit which supports one end of the rocker shaft, and the hydraulic supply portion configured to supply the oil pressure to the other piston includes a second oil passage formed in the rocker housing unit.