PURPOSE: To provide a simple and cheap two-cycle engine of fuel injection type, with which the operating cycles can be stabilized through prevention of misfire even though the operation takes place in the low load range.

CONSTITUTION: In a cylinder 6 a main combustion chamber 10 is formed between a cylinder head 7 and piston 8, while an aux. combustion chamber 12 is furnished which is in communication with the main 10 through a passage. The aux. chamber 12 is equipped with an air and fuel injection valve 18 to inject a mixture 16 of compressed air 14 and fuel 15. The chamber 12 is also equipped with an ignition plug 21.