A microreactor comprises a reaction chamber, into which prescribed materials are introduced, a production chamber, and a channel for connecting the reaction chamber and the production chamber together. A plurality of temperature adjusting devices (e.g., Peltier elements), each of which can be independently controlled in temperature, are arranged at prescribed positions with prescribed distances therebetween on a substrate in proximity to the reaction chamber, the production chamber, or the channel. Herein, the reaction chamber causes reaction of the materials in response to differences of boiling points, differences of state changes, or difference of solubility, thus producing a new substance, which is transmitted from the reaction chamber to the production chamber via the channel while being adequately controlled in temperature.