PURPOSE: To provide an internal combustion engine which is constituted to reduce incurring of an energy loss and improve combustion efficiency.

CONSTITUTION: An internal combustion engine and a drive device comprise an internal engine 2 wherein fuel gas fed from a carburetor 1 is compressed in a compression chamber, compressed gas intermittently fed from the compression chamber is activated, and compressed gas activated in a combustion chamber is burnt to rotate a first drive shaft; an oil pump 4 to feed working oil by a drive force generated by the internal combustion engine 2; and a rotation drive mechanism 5 rotated by working oil fed from the oil pump 4. By circulating working oil between the oil pump 4 and the rotation drive mechanism 5 through a circulation passage 6, a rotation drive force is generated by the rotation drive mechanism 5.