To correctly make a further detailed judgment on a soldered state without being affected by the shape or the like of an electrode.

An image of a soldered electrode is obtained by a camera device 8, and this image is sent to a data processor. A CPU 61 computes a luminance histogram of the image. A neural network 65 is provided and is previously put through learning with the luminance histogram of the image as an input signal and with the visual evaluation value of the soldered state of the electrode as a teacher signal. The luminance histogram of the soldered electrode to be an inspection object is inputted to the neural network 65 to obtain the evaluation value of the soldered electrode.