A quality estimation device for an additive product includes an imaging device configured to illuminate a region including a molding surface during manufacturing of the additive product and image the region, when manufacturing the additive product at a molding position by irradiating with a light beam and a material powder melting and solidifying, a luminance acquisition unit acquires a luminance obtained by quantifying a brightness of a light reflected by at least the molding surface of the region in an image in which the imaging device images the region, and a molding density estimation unit estimates a molding density indicating a density of the material powder in a solidified state after melting based on the luminance of the molding surface acquired by the luminance acquisition unit. The material powder is supplied to the molding position.