PURPOSE: To provide the illumination device for a laser microscope transmitting a light beam as a illuminating beam having uniform intensity distribution of good quality without the disturbance of spacial intensity distribution.
CONSTITUTION: In an illumination device for a laser microscope supplying a light beam 1 composed of plural wavelength beams transmitted from a multi-line laser to the laser microscope, this device is provided with a light beam expanding means 3 inserted in the optical path of the light beam 1 toward the laser microscope, expanding the light beam 1 and making the beam a parallel beam, at least one light quantity varying filter 4, 6a for varying the light quantity ratio of each wavelength component arranged on the optical path of the light beam expanded and made the parallel beam by the light beam expanding means 3, a light beam converting means 8 converrting the light beam 1 passed through the light quantity varying filter 4, 6a to the light beam 1 of the parallel beam having the diameter of transmitting beam after once converging, a special filter 9 arranged on the focal position of the light beam. converting means 8 and removing the disturbance of the spacial intensity distribution of the light beam 1.