Abstract: The present invention provides an apparatus for permitting easy formation of a stable molten region and easy growing of even large-diameter single crystals, with a good-quality of single crystals, of which a floating zone melting apparatus of the infrared-ray concentrated heating type has halogen lamps at one side focal point of four oppositely arranged ellipsoidal reflecting mirrors along orthogonal axes with the inside surfaces thereof as the reflectors, and condensing infrared-rays reflected from the reflectors onto the other side focal point, thereby accomplishing heating, wherein the eccentricity is within a range of from 0.4 to 0.65.