To provide a ship propulsion mechanism performance testing device capable of reducing influence of waves caused by a columnar support for supporting a propeller dynamometer even while the propeller dynamometer is arranged at an upstream side of a propeller.

A performance testing device has a ship propulsion mechanism 2 having at least a propeller 21, a propeller dynamometer 3 for measuring torque transmitted at least to the propeller 21 and thrust generated by the propeller 21, and a columnar support 4 for supporting the propeller dynamometer 3. The propeller dynamometer 3 has a wave control body 5 arranged at an upstream side of the propeller 21 to cover a top part from at least the columnar support 4 to the propeller 21 and arranged at a water level s. The performance testing device 1 has a water tank 11 for making the ship propulsion mechanism 2 sinkable, a rail 12 arranged on a top part of the water tank 11, and a wagon 13 travelable on the rail 12, and the wave control body 5 is supported by the wagon 13 through a supporting member 51.