A personal watercraft includes an inner lid attached in covering relation over a rear portion opening provided in a deck of the personal watercraft, in which a rear edge of the rear portion opening is pressed by a locking member disposed in a locking position thereof to assure the air-tightness of the inner lid, and a rear cover 48 is provided in covering relation over the inner lid. A projection is provided integrally on the locking member which allows attachment of the rear cover when the locking member is in the locked position, but blocks attachment of the rear cover by being sandwiched between the deck and the rear cover, when the locking member is at an unlocked position thereof. A torsion spring (biasing member) which biases the locking member toward the unlocked position is provided between the locking member and the deck. The attaching structure prevents the inner lid from being not attached inadvertently.