To provide a mounting structure of variable turbo driving actuator capable of mounting an actuator on an exhaust turbine-side housing without having the possibility of thermal damage of an oil seal or the like.

A boss part 22 provided on the body 21 of the actuator 20 is allowed to abut on the flange surface 2a of a bearing housing 2 fitted to the exhaust turbine housing 5, and fastened by a mounting bolt 23. The tip part of a drive shaft 15 fixed to the nozzle vane 14 of a variable turbo supercharger 1 is protruded from the flange surface 2a, and the tip part of the output shaft 26 of the actuator 20 is protruded from the body 21. Both the shafts are mutually connected through a lever 40 while providing an axial space 17 between the tip surface 15a of the drive shaft 15 and the tip surface 26a of the output shaft 26. A space part 33 opened around the output shaft 26 is formed by the boss part 22 of the body 21.