This paper describes a bench test evaluation method for vibratory forces caused by a propeller shaft. Most of the vibratory forces are usually generated at the joints of a propeller shaft. They are classified as vibratory forces of axial, radial and moment directions. Axial force can be easily evaluated by measuring the load washer outputs. On the contrary, radial and moment forces can not be analyzed enough clearly even though the outputs are measured, because the load washer for both forces is the same and the outputs depend on the sum of these forces. In this paper, an algorithm for the evaluation method is described. In this method the outputs, as a sum of the forces, are by computation translated separately into kinds of forces which are generated at each joint. The translated results are calculated using an inverse matrix of influence coefficients between the forces and the outputs. Using this method, the evaluation is effective for analyzing the mechanism of the forces.