To provide a variable diaphragm capable of equalizing a light quantity in a view field observed through an imaging optics, and to provide a microscope having the variable diaphragm.

The microscope 10 includes a light source 21, an illuminating optical system 28 for irradiating the light from the light source 21 on an object surface O, an imaging optical system 33 for forming the image of the object surface O by condensing the light from the object surface O, a CCD camera 34 for outputting the image of the object surface O formed by the imaging optical system 33 as a digital image, the variable diaphragm 23 which is disposed in the illuminating optical system 28 and leads at least a part of the light emitted from the light source 21, and a diaphragm control device 36 for changing the ratio of the light passing through the variable diaphragm 23 based on the digital image output from the CCD camera 34.