To quickly and properly drive a piston in a valve gear that changes valve timing with the position-changeable piston and an engagement member contacting with the piston and capable of linked operation concerning the valve gear of an internal combustion engine.

This valve gear comprises first rocker arms 33, 34 supported for rocking motion on a rocker shaft 32 and driven by first cams 31a, 31b to actuate intake valves 11, 12, a second rocker arm 35 supported for rocking motion on the rocker shaft 32, arranged adjacent the first rocker arms 33, 34 and driven a second cam 31c, and a connection changing mechanism 41 changing connection and disengagement of the first rocker arms 33, 34 with the second rocker arm 35 according to a position of the piston 151. The position of the piston 151 is changed with electromagnetic force.