A chord judging method performed by a processor to judge chords of a musical piece, in which the processor estimates plural chord candidates of each of plural parts specified in the musical piece; calculates connection costs, each of which is defined between the chord candidates of adjacent parts of the musical piece; obtains total sums of the connection costs between the chord candidates along plural routes through the musical piece; and selects a route from among the plural routes, which route shows a less total sum of the connection costs of the chord candidates, thereby outputting an appropriate chord candidate of each of the parts along the found route of the musical piece.