Reactor

A reactor using heat exchange between a heat medium and a reaction fluid to cause a reaction of the reaction fluid to proceed, the reactor comprising:

• a heat exchange body including a heat medium channel through which the heat medium flows and a reaction channel through which the reaction fluid flows;
• at least one structured catalyst supporting a catalyst for promoting the reaction of the reaction fluid and removably installed in the reaction channel;
• and
• a holding member including an extending part extending in a direction conforming to an extending direction of the reaction channel and capable of engaging with the at least one structured catalyst, and regulating parts provided in the extending part to regulate a movement of the at least one structured catalyst in the extending direction of the extending part, the holding member being inserted and removed with respect to the reaction channel while holding the at least one structured catalyst.