PURPOSE: To provide the photochemical treating and diagnostic device which manages the irradiation characteristic and irradiation energy quantity of light for irradiation with which a lesion is cast from the front end of a laser probe and is capable of yielding the irradiation energy quantity to enable obtaining of a prescribed treating and diagnosing effect even if the output of the exit light degrades or the wavelength of the light for irradiation deviates from the optimum absorption wavelength of a photosensitive material to be used.

CONSTITUTION: This photochemical treating and diagnostic device is provided with a means 9 for measuring the characteristics of the light for irradiation and a control means 6 which includes a means for managing the irradiation energy quantity and controls the irradiation energy quantity to a prescribed quantity, by which the treating and diagnostic device capable of controlling the irradiation energy quantity directly affecting the treating and diagnosing effect from the exit light output converted to the irradiation characteristic of the light 15 for irradiation to be cast from the front end 13 of the laser probe to the lesion 14 is realized. The device is also provided with a wavelength correcting means which corrects the control target value of the irradiation energy quantity by the wavelength of the light 15 for irradiation.