Valve system for internal combustion engine

A variable valve system includes a transmission mechanism T which transmits a valve actuating force to an inlet valve 11 and which varies a maximum lift amount of the inlet valve 11 and biasing members 60. A sub-cam 40 oscillatably supported on a holder 30 driven by a control member 70 has a roller 43 contacting the inlet cam 15a, a drive cam portion 46 outputting the valve actuating force, and acting portions A contacting the biasing members 60. The acting portions A are provided in the vicinity of the roller 43 so that biased contact points 45a1, 45bl are positioned nearer to a cam contact point 43a than an oscillation center line Ls and that an acting-line L1 of a biasing force is superposed on the roller 43 as viewed in the direction of the oscillation center line Ls.