1. A scoring device comprising: an acquisition unit that acquires image data in which a singer is photographed; a detector that detects a feature associated with an expression or a facial motion during singing as a facial feature of the singer from the image data acquired by the acquisition unit; a calculator that calculates a score for singing action of the singer based on the feature detected by die detector; and an output unit that outputs the score, wherein a target expression is previously defined with respect to music being sung by the singer as a target feature, wherein the detector detects the facial feature of the singer in a scoring period that is of at least part of a period of the music being sung, and wherein the calculator calculates the score as a sum of lengths of periods in which the facial feature matched with the target feature detected in the scoring period.