PURPOSE: To ease transportation or storage and to improve maneuverability of a catamaran in which a pair of float body are connected together by beams, by forming each float body with a bag body capable of being folded and by attaching a metal plate to the aft end surface of each float body for holding a rudder.

CONSTITUTION: A pair of float body 1 consist of bag bodies, made of waterproof material like rubber, whose insides are filled with compressed air to maintain the shape. Each float body 1 is connected with each other by making the ends of each beam 2 and 3 to penetrate locking pieces 13 provided at both fore & aft and outer & inner sides of each float body 1, so as to have each fload body 1 connected with each other. Sleeves 41 provided at both ends of a connecting rod 42 are made to penetrate beams 2 and 3 which are connected together through a connecting member 4. At the crossing point between the forward sleeve 41 and a connecting rod 42, a mast holder 43, into which a mast 6 is inserted, is fixed. At the aft end of each float body 1, a metal plate 8 is fixed by means of adhesive cloth 81 so that the metal plate 8 holds a rudder plate 9 that is operated by an operating rod 93 via a connecting rod 92.