There is provided an apparatus of inspecting a packaged state by scanning a packaged printed circuit board with a fine light beam and detecting reflection beams of the fine light beam in a plurality of directions. A fine light beam emitted from a light source is scanned on the packaged printed circuit board substantially vertically thereto by means of a polygon mirror and a light projection f.theta. lens. An optical path correcting system receives reflection beams scattered from the packaged printed circuit board and corrects optical paths of the reflection beams. The correction is done in such a way that reflection beams having constant directional vectors regardless of the change of the scanning position of the fine light beam are received and guided to light receiving positions complying with a height at a scanning position on a plurality of photoelectric conversion devices. Through this, the packaged state of parts is inspected at a high speed, with high accuracy and over a wide range without expanding the light receiving area of the photoelectric conversion device and without causing characteristics of triogonometrical survey to change with the scanning position.