PURPOSE: To obtain a hydrogen engine removing preignition and backfire.

CONSTITUTION: A first cylinder, a second cylinder, and a third cylinder are made for the purpose of using mixture suction 1 of energy in a crankcase 9 as working stroke, and respective cylinders are constituted so as to work each other. Moreover, in A row, the first cylinder is made to be in a mixture suction stroke 1, the second cylinder in an ignition and explosion stroke 3, and the third cylinder in an air suction stroke 5. The other end part of a connecting pipe 17 constituted in connecting one end part of a crankcase 9 of the third cylinder in the air suction stroke 5 is connected to a connecting end part of a hydrogen intake pipe 11 in upper part of a cylinder chamber 7, and this engine is constituted so as to intake air in the crankcase 9. Moreover, the other end part of a connecting pipe 15 connected to one end part of an air intake pipe 10 in upper part of the third cylinder in the air suction stroke 5 is connected to the crankcase 9 of the first cylinder in the mixture suction stroke 1 to be constituted. A three cylinder six-cycle hydrogen engine connected an intake pipe 24 to the bottom face of the crankcase 9 to be constituted is made.