To enable diagnosis and treatment to be performed using the same laser beam in a laser-beam chemical treatment.

A laser beam L is emitted from a laser beam source 8 via a light guide F1 toward a focus part where a photosensitizer is accumulated specifically. Phosphorescence emitted from an active enzyme produced by a photochemical change between the laser beam and the photosensitizer is introduced by a light guide F3, is subjected to spectral diffraction by a spectroscope 38, is photographed by an infrared high-sensitivity camera 24, and transferred to a monitor device 6 to display a spectrum distribution of the phosphorescence. Also, the phosphorescence is introduced by a light guide F4, is photographed by an infrared high-sensitivity camera 22, and transferred to a monitor device 4 to display images of the range of generation and the strength distribution of the phosphorescence. The spectrum distribution and the images or the range or generation and strength distribution of the phosphorescence allow checking the focus part and its range and diagnosing the degree of wetting, etc. During a treatment, a laser beam L of the same wavelength from the laser beam source 8 is applied to the focus part via the light guide F1.