To provide an engine vibration suppressing device reducing the vibration even in an engine without any igniter or with the igniter in failure.

This engine vibration suppressing device is provided with combustion chambers 24 installed for every multiple cylinders 17-20, multiple pistons 22 individually operating by the heat energy generated in the respective combustion chambers 24, and a crankshaft rotatably constituted about the axis, connected to the respective pistons 22 in axial different positions, and rotated by the kinetic energy transmitted from the respective pistons 22. The volumes of the combustion chambers 24 are differed according to the respective cylinders 17-20.