Abstract: Provided is the prefabricated body using a module for a roaster according to an embodiment of the present invention, the prefabricated body including: a module including a module body provided with a fastening hole on one end side surface thereof, a first coupling groove provided in a longitudinal direction at a side of the module body, and a second coupling groove provided in the longitudinal direction at an opposite side of the module body at an arbitrary angle with the first coupling groove; a polygonal body with both ends open configured by module plates detachably coupled correspondingly with the first and second coupling grooves; a door openably installed at an opening at a side of the polygonal body; and a side plate installed at one opening at an opposite side of the polygonal body so as to face the door by a fastening member coupled with the fastening hole.