To provide a three-output-shaft internal combustion engine in which mixed gases are combusted in the same combustion chamber in an internal combustion engine device, mechanical motive power is imparted to a pair of pistons by the combusting gases exploded and expanded by the combustion to produce rotational force in a crankshaft, and scavenged high-speed, high-pressure combusting gas (actuating gas) is utilized to drive a gas turbine and produce rotational force in a turbine shaft.

The three-output-shaft internal combustion engine employs a means as the three-output-shaft internal combustion engine in which mixed gases are combusted in the same combustion chamber, the combusting gases exploded and expanded by the combustion impart mechanical motive power to a pair of pistons positioned in a substantially opposing relationship at a predetermined angle (90-160 degrees), the mechanical motive power is converted in a rotational direction using a crank mechanism to produce rotational force in right and left crankshafts, scavenged high-speed, high-pressure combusting gas (actuating gas) is utilized to drive a gas turbine, and rotational force is also produced in a turbine shaft of the gas turbine.