PURPOSE: To enable irradiation of desired laser beam power with a small and simple system by application of a laser device which combines transistor laser and an optical lens which collects laser beams and a light introducing fiber for laser beam in the center hole of an injection needle, with one end of the injection needle cut sharply.

CONSTITUTION: To a base 8, a transistor laser 5 and an optical lens 6 are applied, with one end of the base 8 made cylindrical. A cover 7 which is bound with a cable 2 is fixed to a base 8 to constitute a laser applying device 3. A laser needle 4 consists of an injection needle 9 and an optical fiber 10. One end of the injection needle 9 is cut sharply to permit easy insertion into the body, while to the other end an applying part 9a is attached to make application of the base 8 to the end 8a easy. From hygiene consideration, the optical fiber 10 and the center hole of the injection needle 9 are preferably in sealed condition.