In a personal watercraft with a watercraft body including a hull forming a bottom portion and a deck covering the hull from above, a magnet box is integrally combined with a battery storage tray. The watercraft also includes an engine disposed within the watercraft body, and a saddle-type seat disposed above the engine. A magnet box, including a main box body and a lid member, sealingly stores an electromagnetic starter switch therein, and is disposed in front of a battery storage tray, in order to reduce the distance between the magnetic starter switch and a starter motor. The main box body is formed integrally with a battery storage tray which is disposed in back of the engine and fixedly disposed on a floor portion of the watercraft body. The lid member is adapted to sealingly close the main box body of the magnet box in a fluid-tight manner.