To solve the problem that the injected fuel becomes the droplet hard to be evaporated and that the mixing with the air is insufficient and that the excellent combustion is hard to be obtained at a high temperature of the top surface of a piston when injecting the fuel toward the piston top surface in a cylinder fuel injection type internal combustion engine.

In a cylinder-fuel injection type internal combustion engine provided with an oil jet 17 for injecting the lubricating oil OL1 to the piston back surface to cool a piston 9, a target temperature range of the piston top surface temperature is set from a boiling point of the fuel to a temperature for lowering the wettability of the piston top surface and the fuel adhered to the piston top surface, and the injection oil quantity of the oil jet 17 is controlled so that the temperature of the piston top surface exists within the target temperature range during the operation of the internal combustion engine.