The present invention is related to a quantitative powder-providing module, adaptive to a 3D prototyping mechanism, at least includes: a powder-providing tank, which is used for storing a constructive powder and having a powder-dropping opening; and a powder-propelling roller located inside the powder-providing tank and having a plurality of recesses for receiving the constructive powder; when one of the plurality of recesses corresponds to the powder-dropping opening, the constructive powder received in the corresponding recess is output through the powder-dropping opening; wherein each of the plurality of recesses has plural sections, and the amount of powder received in each of the plural sections of the recess is increased from the center of the recess, toward the two sides of the recess.