A microreactor (1) comprises a vacuum casing (2), a microreactor proper (4) located in a vacuum-tight cavity (3) in the vacuum casing (2), and a getter heat-generation substrate (6) positioned on at least one surface of the microreactor proper (4). The microreactor proper (4) has a feed inlet (19a) connected to outside the vacuum casing (2) by way of a feed supply pipe (5A) and a gas outlet (19b) connected to outside the vacuum casing (2) by way of a gas discharge pipe (5B). The getter heat-generation substrate (6) comprises a substrate (7), and a heat generator (9) and a getter material layer (10) that are located on the substrate (7) alternately in mutual non-contact fashion.