A ride plate positioning mechanism for a personal watercraft can reduce the burden on an operator during assembly, and can also raise manufacturing productivity. In a ride plate positioning mechanism 30 of a personal watercraft 10, a portion of a bottom wall 15a of a stern 15, that is located below a water jet propeller 17, is formed from a ride plate 31 removable from a craft body 11. Further, a pair of left and right positioning projections 32, 32 are formed integrally on the ride plate 31, while a pair of left and right tab stops 33, 33 corresponding to the positioning projections 32 are provided on the craft body 11 side.