An aesthetic or medical laser system is disclosed. The laser system includes: a spectrometer configured to measure a spectrum of light which is generated when body tissue is irradiated with a laser for beauty or medical care； a spectrum data comparison unit configured to compare the spectrum of the generated light measured by the spectrometer and a disease diagnosis reference spectrum data DB； and a disease diagnosis unit configured to determine whether there exists a disease in the body tissue based on a result of comparing by the spectrum data comparison unit.
