A reaction apparatus includes: a chemical reaction unit for causing a reaction of a reactant by being set to a predetermined temperature and by being supplied with the reactant, a heat insulation package for housing the chemical reaction unit therein, an abnormality detector for detecting at least one of a temperature abnormality of the chemical reaction unit and the heat insulation package, and a cooling unit for flowing a cooling fluid to the chemical reaction unit to stop the reaction according to a detection result by the abnormality detector. In the reaction apparatus, the leakage of heat inside the reaction apparatus to outside is prevented when abnormality occurs to the chemical reaction unit and the heat insulation package.