PURPOSE: To enable uniform radiation of far infrared rays in the horizontal direction around a glass cylinder, by a method wherein far infrared layers are formed at each stage around the glass cylinder raging from a lower stage to the upper part thereof, a ratio of a total area occupied by far infrared layers to the peripheral surface of the glass cylinder at each stage is gradually decreased from a lower part to an upper part.

CONSTITUTION: A glass cylinder 13 is equally divided into a lower stage region Ea, a middle stage region Eb, and an upper stage region Ec, and the same number of far infrared layers 20 is formed to each of the regions Ea, Eb, and Ec. Areas of the far infrared layers 20 at the regions Ea, Eb, and Ec are Sa, Sb, and Sc, respectively, and a relation between the areas is set to Sa>Sb>Sc. In this constitution, by offsetting between the temperature difference of the glass cylinder and a difference between the total area of the far infrared layers and that of the peripheral surfaces at each of the regions Ea, Eb, and Ec, a radiation amount of far infrared rays from each of the far infrared layers 20 is about uniformized. Thereby, the portion above the waist of a person, seating in front of a combustion cylinder 3 for warming himself thereby, is uniformly warmed to provide an ideal state in that the person warms himself thereby.