To provide an apparatus capable of simply and accurately measuring the number of colonies excellent in reduction in labor, useful for a sanitary survey of a food, etc., by taking the whole image of a Petri dish by a CCD camera under a specific condition.

This apparatus for measuring the number of colonies is equipped with a CCD camera so as to photograph a determined part of the whole cultured Petri dish 2 and is constituted so as to input an image within a range of the determined part of the whole Petri dish 2. The apparatus has a structure for rotating the Petri dish 2 in the circumferential direction or moving in the vertical or horizontal direction or for rotating the CCD camera in the circumferential direction or moving in the vertical or horizontal direction. The image of the whole Petri dish 2 is taken by the CCD camera by rotation or movement in the direction to measure the number of colonies 3.