To provide a method and a device capable of cleaning the cloth surface of a futon efficiently by applying wash water to the inside of the futon without impregnating it.

A suction mechanism part is brought into the proximity of or contact with the lower side surface of a futon 1 to move the lower side cloth of the futon 1 downward. A rotating brush 3 is brought into contact from below with the cloth of the futon 1 moved downward, and wash water 41 is emitted from below toward a part in contact between the rotating brush 3 and the futon 1. By this, the wash water 4 is applied to the inside of the futon 1 without impregnating it to clean the surface of the futon 1. Or a rotating brush 3 which comes into contact with and cleans the lower side cloth of a futon 1 moved downward by suction by an air suction device 2 for sucking the lower side cloth of the futon 1 and a wash water emitting device 4 which emit wash water 41 upward are provided at the lower part of a supporting base, which is a supporting object to the futon 1. The futon supporting base, the suction opening 21 of the suction device 2, the brush part of the rotating brush 3, and the wash water emitting device 4 are relatively movable while each vertical position is maintained approximately constant with respect to each other. By this, the surface of the futon 1 is cleaned by applying the wash water 41 to the inside of the futon 1 without impregnating it.