To provide an engine testing device for efficiently absorbing vibration generated by an engine as compared with a conventional engine testing device.

The engine testing device 10 comprises a shaft 20; a motor 42 for rotating the shaft 20; and a chuck unit 50. The chuck unit 50 has three nib members 58a, 58b, and 58c arranged with the axis of the shaft 20 as a center. The chuck unit 50 moves respective nib members 58a, 58b, and 58c between a first position engaged to an engine rotary shaft and a second position alienated from the engine rotary shaft. Then, the shaft 20 and the nib member unit 50 are connected via a rubber coupling 22 and a damper section 60.