Abstract: A heat storage mat for a bed is constructed to provide a heating intensity, a heat insulation and a cushioning effect which are adjusted to meet various conditions which are required for various parts of the driver's body to insure a comfortable sleep. The heat storage mat includes a plurality of heating elements arranged in a row in a longitudinal direction of the mat. Each of the heating elements is composed of a flat bag filled with a latent heat storage agent and an electric heater unit disposed on an underside of the flat bag. The quantities of the latent heat storage agents associated with the respective heating elements increase successively in a direction from a head side toward a leg side of the mat. A plurality of heat insulating cushions are disposed on upper surfaces of the corresponding bags. The heat insulating cushions have thicknesses which vary in inverse proportion to the quantities of the latent heat storage agents of the respective bags.