Abstract: A variable trimaran that uses natural power has an outer hull, which is capable of ensuring stability with respect to a center hull in the middle thereof. The variable trimaran can be selectively expanded and contracted in the horizontal and vertical directions thereof. The variable trimaran includes a sail unit, which uses wind power, and a solar power generation unit so as to enable efficient long-term sailing without the use of fossil fuel. To this end, a horizontal and vertical adjustment units are provided for adjusting the position of the outer hull, and the solar power generation unit and the wind power sailing unit are used such that the position of the outer hull can be freely adjusted with respect to the center hull and efficient long-term sailing is enabled without the supply of an oil energy source due to the use of sunlight and wind power as power sources.