A method for forming stable pleats on a fabric composed of a polylactic acid yarn of 100 mass % without causing decrease in physical properties of the polylactic acid yarn includes preparing a fabric composed of a polylactic acid yarn of 100 mass %. The fabric may be a raw fabric such as a woven raw fabric or a sewed product into which a raw fabric is sewed. The sewed product may be one in which part of clothing is sewed, or a final product. The fabric is folded up, and imparted a pressure in the folded state. Specifically, the folded fabric is passed under a suitable line pressure between a pair of rolls whose surfaces are heated in atmospheric ambience. The surface temperature of the rolls is about 100 to 130° C. As described above, a pleated fabric such as pleated clothing whose folded-up portion becomes stable pleats can be obtained.