To accurately and easily measure a thrust.

A lower part of a stern part installed with a water jet pump 4 is manufactured separately from a main hull model 2 as a stern portion model 3, in a hull model 1 of a water jet propelled ship. The stern portion model 3 is held to the main hull model 2 displaceably along a longitudinal horizontal direction via guide rails 9 and a guide block 10. A load cell 5 is attached to the main hull model 2, and a rear end of the load cell 5 is connected to an inner upper end position of a rear end wall of the stern portion model 3 via a longitudinal-directional connecting member 11. The thrust generated by a reaction of a water jet jetted rearwards by driving the water jet pump 4 is transmitted from the stern portion model 3 to the main hull model 2 via the connecting member 11 and the load cell 5, to advance the hull model 1, and the thrust acting actually as a driving force is directly measured therein by the load cell 5.