To provide a seat structure of a personal watercraft capable of accommodating the seat in the hull or taking it to outside the hull according to the maneuvering condition of the boat operator.

An accommodation space 22b is formed over an engine hatch 22a installed in the hull 10a. An opening 24a is formed in the rear end face of a hatch cover 22 to enable the seat 21 to be accommodated in the space 22b from the opening 24a, and the rear end face of the seat 21 is allowed to constitute part of the hatch cover 22 when the seat 21 is accommodated in the space 22b. Rails 25b and 25c are laid in the space 22b, and the seat 21 is made movable between the inside and outside of the space 22b while it moves fore and aft along the rails 25b and 25c. Also it is arranged so that a supporting member 39 is engaged with the bottom of a guide groove 34 for supporting the seat 21 when the seat 21 protrudes from the hatch cover 22.