The invention relates to a reactor system, comprising a heat-exchange unit and a reaction unit that are assembled together into a structure. The heat-exchange unit has a plurality of plate or corrugated-plate heat exchangers, and is formed so as to be attachable/detachable to/from the reaction unit and insertable into the latter. Accordingly, a catalyst may be attached to a heat-transfer surface of a heat exchanger by a washcoat method or the like, thus maximizing heat-transfer efficiency and enabling the easy removal or reattachment of the catalyst at the end of the lifespan of the catalyst.