A variable valve mechanism of an internal combustion engine capable of changing at least one of two valve physical quantities, i.e., valve operation angle and valve lift, has a valve lift adjustment mechanism that adjusts the at least one valve physical quantity with a higher precision in a region where the at least one valve physical quantity is relatively small than in a region where the at least one valve physical quantity is relatively large. Therefore, a size increase of the variable valve mechanism can be avoided, and the mechanism can easily be incorporated into the engine.