Provided is a microscope equipped with an automatic focusing mechanism, comprising an illumination light source; an objective lens for focusing first light emitted from the illumination light source onto an object to be detected; an illumination light source for imaging the first light that is reflected by the object to be detected and passes through the objective lens; and a focal-point detector for detecting a positional shift of a microtiter plate from a focal position of the objective lens, wherein the focal-point detector includes a focal-point-detection light source for emitting focal-point-detection light serving as second light, a focal-point detection light acquisition unit on which the focal-point-detection light is focused, and a region setting unit which can set an in-focus assessable region of the focal-point-detection light acquired by the focal-point detection light acquisition unit to any position on the focal-point detection light acquisition unit.