To divert a futon to a knee-covering warmer or a coverlet for a short-leg table, hanging it down from the rear of the short-leg table, by putting the mattress under the short-leg table on the knee when a user feels a chill suddenly by the change of air temperature when sitting at the short-leg table.

This futon 3 serving for both mattress and coverlet is provided in advance with the first openings 4 at the sections where the feet 2 of a short- leg table stand, and a user uses it as a knee-covering warmer, by shifting the futon serving for both mattress and coverlet onto the knee along the feet 2 of the short-leg table and sitting under it when he feels a chill. Moreover, to enable the futon serving for both mattress and coverlet to be attached also to the rear of the short-leg table, this is provided with a second opening 5 also at the center of the futon serving for both mattress and coverlet, and the user uses it also as a warming coverlet under the shortleg table by attaching the opening to the rear of the short-leg table through a fitting tool such as a velvet type of fastener, or the like.