To provide a fuel gas control mechanism for surely blocking up a fuel gas supply hole even if fuel gas mixed with a fine foreign matter is used, and an internal combustion engine for improving output efficiency and durability by using this fuel gas control mechanism.

This fuel gas control mechanism 10 has a fuel gas passage 9 for supplying the fuel gas to a combustion chamber of the internal combustion engine and a fuel gas adjusting valve 13 for controlling a supply quantity of the fuel gas by opening-closing the fuel gas supply passage 9, and is characterized by comprising a hydraulic cylinder 11 for driving the fuel gas adjusting valve 13, a hydraulic fluid adjusting valve 24 for controlling the inflow and the outflow of the hydraulic fluid being driving force of the hydraulic cylinder 11 and a control part 27 for controlling operation of the hydraulic fluid adjusting valve 24.