Abstract: This pre-chamber type engine is provided with pre-chambers formed in the cavities in piston bodies, and head plates consisting of a material of a high thermal resistance the thermal expansion coefficient of which is substantially equal to that of the piston bodies and fixed to the piston bodies. The fuel injection nozzles project into the insert bores made in the head plates when the pistons are in positions in the vicinity of the top dead centers. The communication ports formed in the head plates extend in the portions thereof which are around the insert bores diagonally with respect to the axes of cylinders, and are spaced from one another in the circumferential direction thereof.