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 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 when the enabling the easy removal or reattachment of the catalyst at the end of the lifespan of the catalyst.