To assemble a belt including a plurality of elements and a ring for fastening the element efficiently. A belt assembling apparatus for fastening a plurality of plate-like elements being juxtaposed in a same orientation annularly by a ring includes a load applying mechanism, which applies a load to the ring or to the elements which have already been fastened by the ring during a process of fastening the elements sequentially by the ring, thereby widening a clearance in an array of the elements being fastened by the ring. Therefore, the clearance to which the last piece of the element to be fastened by the ring is inserted can be widened relatively so that the element is allowed to be inserted into the clearance easily.