1. A microscope system comprising: an optical microscope for observing a test object; and a computer connected to the microscope; wherein the microscope comprises, an illuminating optical system that illuminates the test object with illumination light from a light source under predetermined illumination conditions, an imaging optical system that forms an image of the test object on the basis of light from the test object, and an image sensor that detects the image of the test object formed by the imaging optical system and outputs an image signal, and wherein the computer comprises, an image analyzing unit that acquires an image feature amount of the test object on the basis of the image signal detected by the image sensor, a comparison unit that compares the image feature amount of the test object with image feature amounts of a plurality of sample test objects and specifies an image feature amount of a sample test object closest to the image feature amount of the test object, and a setting unit that sets illumination conditions of the illuminating optical system on the basis of an illumination state suitable for observation of a sample test object having the image feature amount specified by the comparison unit.