Abstract: This invention relates to medical engineering, more particularly, to therapeutically applicable light-irradiating devices used for treatment of skin diseases, as well as for generating vitamin D3 and preventing various forms of osteoporosis. In addition, the device can find application at beauty shops and sunless-tanning studios for cosmetic purposes. A technical problem to be solved by the present invention resides in increasing the efficiency of the device. The problem is solved due to reducing the amount of the lamps to ‘n’ and substituting the plain circular cylinder-shaped reflector by a reflector comprised of 2n alternating areas of involute cylinder-shaped surfaces of two types integrated into a single surface, the evolutes of said surfaces are closed curves which limit the convex transverse sections of the lamp and absorber in contemplation, respectively, which reflector is interposed between the lamps and the solarium body.