Provided are a plastic microfabricated structure, and a microfabricated thermal device, a microfabricated reactor, a microfabricated reactor array and a micro array using the same, which may be applied to a bio chip, and the present invention may fabricate the plastic microfabricated structure for providing a heating region by means of insulating plastic, which has a thin thickness, flatness enough to allow a photolithography process to be performed, thermal isolation in its some or total area, and a small thermal mass, and on top of the heating region of the plastic microfabricated structure, a heater, a temperature sensor for sensing a temperature, an electrode, and an electrode pad are formed to thereby fabricate the microfabricated heating device, whereby element may be readily fabricated at a low cost, and the heating region is formed of a plastic thin layer, so that uniform temperature control is possible even with a low power, and various samples may be thermally treated at a fast speed to obtain their reaction and analysis.