A built-up drum includes a drum body and two drum faces. The drum body includes a plurality of body components of which each includes a base, two jammed portions, an inserting portion and an insertion slot. One end of the base extends to form the inserting portion and the insertion slot is formed in the other end of the base. The inserting portion of each body component is inserted into the insertion slot of another body component, so that the body components define a profile of the drum body. A top face and a bottom face of the base respectively extend to form the jammed portions for being jammed on the drum faces. Accordingly, the present invention can simplify structure components, lighten the drum, and be easily disassembled and assembled for convenient carry. Further, the drum body is expandable for having different sizes, which is convenient for use.