PURPOSE: To produce a skinned processed product having excellent qualities by swelling only thin periderm and epidermis of yam and raising yield by mechanization.

CONSTITUTION: Cleaned yam is treated with cellulase in the presence or absence of an alkali, only light brown thin periderm and epidermis of the yam are swollen without lowering qualities of inside flesh. The periderm and epidermis of yam are skinned by a simple mechanical operation. The yam thus processed is cut into fine strips or ground in a skinned state as it is and packed.