There is provided a method for forming a three-dimensional decoration on a wall surface, wherein the method comprises: drawing a sketch on the work wall-surface; installing a crack-prevention member on the work wall-surface to suppress a separation between the three-dimensional decoration and the wall surface, wherein the crack-prevention member is disposed in a first region corresponding to the sketch; plastering a cement-mortar in the first region on the work wall-surface so as to embed the crack-prevention member in the cement-mortar, thereby to form a cement-mortar relief; three-dimensionally engraving a front face portion of the cement-mortar relief to form a cement-mortar relief-type decoration as the three-dimensional decoration; and coloring the cement-mortar relief-type decoration using a mixture of silicon as a binder and coloring pigments.