To control uneven density of pre-mixed gas in a self-ignition so that a suitably operable region expands to both a low load side and a high load side in a premixed compression self-ignition type internal combustion engine.

In this premixed compression self-ignition type internal combustion engine which comprises two or more intake ports In 1, In2, a flow rate adjusting valve 12 for changing a flow rate passing through the intake port In 2 is arranged in one of the intake port In 2 of the intake ports, and a fuel injection hole 10 is arranged only in the intake port which is arranged with the flow rate adjusting valve 12. The fuel injection hole 10 is positioned on the downstream side of the flow rate adjusting valve 12. The flow rate adjusting valve 12 is controlled so as to maintain any opening other than a full opening at the time of fuel injection from the fuel injection hole 10. The flow rate adjusting valve 12 is controlled so that the opening becomes larger than at the lower loading timing in the high loading timing, and the opening becomes smaller than at the low rotating timing in the high rotating timing.