To compensate for ununiformity of light flux density accompanying the deflection of optical path by picking up both mask alignment mark and work alignment mark with a camera while irradiating the picking-up area with the scattering beam.

The scattering beam is incident to the mask alignment mark 1a and work alignment mark 4 at the picking-up position and also lights the range sufficiently wider than the regions of the mask alignment mark 1a and the work alignment mark 4. In this case, the lighting beam is incident to the photosensitive material film 3a at the position of the work alignment mark 4 from every angle. Thereby, even if the light incident part of the photosensitive material film 3a is recessed, the light is refracted in every angle when the light passes the recess of the photosensitive material film 3a. Thereby, the density of light flux that is incident to a CCD camera is almost uniformed, except for the part corresponding to the mask alignment mark 1a.