The present invention relates to a solid foaming bath additive with which, when having a bath, it is possible to directly and sustainedly feel satisfactory bubbles on the skin. The solid foaming bath additive comprises a carbonic acid salt and an organic acid, and is an approximately columnar object which has an upper surface, a lateral surface, and a bottom surface and has depressions in the upper surface, at least some of the ends of the depressions extending to the lateral surface to form recessed parts in the lateral surface, and in which the upper surface forms bubbles upon contact with bath water, wherein when the solid foaming bath additive is cut along an imaginary cross-sectional plane which is parallel apart, by 1 mm toward the bottom surface, from an upper circumscribed plane that includes at least three points of contact located on the upper surface and that is located most apart from the bottom surface, then the horizontally projected area of the portion of the solid foaming bath additive which lies in the imaginary cross-sectional plane accounts for 5-70% of the horizontally projected area of the whole solid foaming bath additive.
