PURPOSE: To improve the processing ability of a device by positioning a substance to be inspected so that an area to be inspected which is previously detected at low magnification may be is a high-magnification observing visual field and then performing detailed inspection at high magnification.

CONSTITUTION: Low-magnification and high-magnification observing objective lenses 5 and 6 are mounted in an electrically driven revolver 4 and the switching of the low magnification and the high magnification is automatically performed by the revolver 4. First, a spinneret 1 is roughly positioned on X-Y axes driving stages 2 and 3 by a guide. Next, the observing magnification of a microscope is switched to low one by the revolver 4 and the stages 2 and 3 are driven to be positioned at the radius position where the spinning hole of the spinneret 1 exists in a low-magnification visual field. In such a case, the spinneret is moved by the stages 2 and 3 so as to scan the concentric circle of the spinning hole with the low-magnification visual field to detect the position of the spinning hole, and then the accurate position of the spinning hole is obtained. The observing magnification is switched to high one by the revolver 4 and the stages 2 and 3 are driven to perform inspection by the high-magnification image of the spinning hole.