PURPOSE: To ease transportation or storage of a catamaran in which a pair of float body are connected together by beams and to improve the sailing performance thereof by forming each float body with a bag body capable of being folded and by providing each float body with a center board in a rotatable manner.

CONSTITUTION: A pair of floar body 1 are connected with each other by beams 2 and 3 located at both fore and aft parts of each float body 1, while the beams 2 and 3 are connected together by means of connecting members 40 and 4 at the ends and the middle point of the beam 2 and 3, respectively. The connecting member 40 is fixed to each float body 1 by means of a band 7, and a mast 6 of a sail 5 is supported on the connecting member 4. Each float body 1 consists of a bag body which is made of water-proof material like rubber and filled with compressed air to maintain the shape. A center board 10 is projected from the bottom of each float body 1. This center board 10 is inserted into a slit 13, which passes vertically through the float body. A pin 15 of a holding member 14 fixed to the bottom of the slit 13, is fitted into a recessed portion 16 of the center board 10 so that the center board 10 may be held in a rotatable manner.