A cancer diagnosis and treatment device comprising a solid-state laser generator such as an Nd-YAG laser, an alexandrite laser, or titanium sapphire laser for emitting a first laser beam having a first wavelength, a harmonic generator for generating higher harmonic laser beams of the first laser beam and outputting one of the higher harmonic laser beams, and an optical parametric oscillator for converting the harmonic laser beam outputted from the harmonic generator into second and third laser beams suitable for the cancer diagnosis and treatment, the second laser beam having a second wavelength stimulating a sterilizing photochemical reaction between the photosensitive material and the cancer foci to perform the cancer treatment and the third laser beam having a third wavelength inducing fluorescence inherent to the photosensitive material to enable the cancer diagnosis, an endoscope for guiding the second and third laser beams emitted from the laser beam source to the cancer foci and transmitting an image of the fluorescence of the photosensitive material to an outside of the body, and a cancer observing unit having a screen for receiving the image of the fluorescence of the photosensitive material al transmitted through the endoscope unit and displaying the image on the screen to thereby perform the cancer diagnosis.