Disclosed is a variable valve mechanism for an internal combustion engine. The variable valve mechanism accurately adjusts the valve operating angle although its structure is simple. The variable valve mechanism includes a control pin 48, which is inserted into a pin insertion hole 38 in a control shaft 16; a bearing hole 44, which is formed in a control member 26; and an adjustment pin 50, which is rotatably supported by the bearing hole 44. The adjustment pin 50 comes into surface contact with the control pin 48 to inhibit the control member 26 from rotating relative to the control shaft 16. The valve operating angle is adjusted by replacing the adjustment pin 50 with another having a different dimension B. Such adjustment pin replacement changes the distance A between the center line of the bearing hole 44 and the center line of the control pin 48, thereby changing the relative angle θ between the control shaft 16 and control member 26. When the adjustment pin 50 rotates within the bearing hole 44, the surface contact between the adjustment pin 50 and control pin 48 is maintained irrespective of the magnitude of the relative angle θ.