PURPOSE: To inclination, irregularities, and the like of an object by determining the center of gravity of imaging light point on an imaging surface and measuring positional shift of the center of gravity.

CONSTITUTION: An object W is placed at a horizontal reference position and light is projected thereon from a light projector 2. A camera 3 picks up an image of the object W and retrieves the center of gravity G on an imaging surface thus determining a reference position. When the object moves to a position Wa inclining by an angle θ, the surface T irradiated with the light projector 2 moves to Ta and the center of gravity G of the imaging surface S moves to C. Assuming the moving distance of the center of gravity as (c), elevating distance (h) of measuring point is measured. Assuming the central position of lens is A, and the positions corresponding to the center of gravity G on the irradiated surfaces T and Ta are F and D, (c) can be determined through measurement because the length m:k is known. Since <δ <β can be calculated, each dimension of ΔABF can be calculated. Furthermore, since <α is known, one side BF and one angle <ABF of ΔDBF can be calculated and, thereby, the sides DF, DB and the height (h) can be calculated. The measurement is repeated while moving the object Wa thus discriminating inclination or irregularities and determining the degree of irregularities.