To provide a variable valve mechanism of an internal combustion engine capable of changing a maximum lift amount and a lift period of an engine valve, and a valve timing according to an engine operating condition and also capable of suppressing contact between the engine valve and a piston.

The variable valve mechanism of an internal combustion engine 100 includes: a maximum lift amount changing mechanism 300 which changes a maximum lift amount and a lift period of an engine valve; and a valve timing changing mechanism 200 which changes a valve timing of the engine valve. The valve timing changing mechanism 200 includes a lock mechanism 500 which restricts a rotary phase change between a cam sprocket and a cam shaft 120 by fitting a lock pin into a lock hole. The maximum lift amount changing mechanism 300 includes a passage switching mechanism which switches operating oil passages so as to fit a lock pin into a lock hole, if a control shaft 340 is at a nearer side on which the maximum lift amount is increased, than a reference position.

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