To simplify the fixing structure of a leg to a base plate, to improve the fixing strength of the leg and to simplify the blow formation of a desk member together.

A kotatsu (Japanese foot warmer with frame and coverlet) base plate 2 is formed by blow-forming thermoplastic plastic. At the leg mounting part 3 of the plate 2, a leg fixing recessed part for fitting and fixing the base part 5 of the leg 4 is formed in one body with the kotatsu base plate. Then concerning the leg 4, its main body part 11 is constituted to be freely elevating and declining in a vertical posture and in a posture bent nearly at 90 degree with respect to the part 5 of the leg 4. The leg 4 is provided with elevating and declining posture regulating structure regulating each elevating and declining posture to the vertical posture and the posture bent nearly at the 90 degree.