<p>A usable coin judgment device is provided with a brightness histogram making-up means that sums up a brightness value of each pixel for every pixel string in a predetermined direction (horizontal direction, for instance) in a predetermined area of a coin image picked up by an image picking-up means to calculate a brightness frequency and makes up a brightness histogram, and an absolute differential value summation calculation means that calculates an absolute differential value summation that is a summed-up absolute values of differences between neighboring brightness frequencies of the brightness histogram for a predetermined interval of the brightness histogram. The usable coin judgment device judges if a coin under inspection is a stained and unusable one based on the comparison of the absolute differential value summation with a predetermined threshold value.</p>
