PURPOSE: To make it possible for a fuel injection type internal combustion engine to be lightweight and compact to reduce cost by setting the so-called complete penetration force of a jet lower within a range necessary for the diffusion of fuel, and setting the fuel pressure lower.

CONSTITUTION: In a fuel injection type internal combustion engine in which a combustion chamber 29 is made up of a cylinder head 23, a cylinder body 22, and a piston 26, a scavenging port and exhaust port 44 are formed in the cylinder wall 22a, and an injector 61 is mounted to the cylinder wall 22a in order for a fuel to be injected from the injector 61 into the combustion chamber 29, the injection speed of the fuel injected from the injector 61 into the combustion chamber 29 is kept in a range from 10m/s to 30m/s.