PROBLEM TO BE SOLVED: To provide an organic field-effect transistor type gas sensor which can achieve both the excellent detection sensitivity of gas and the desorption of gas; and a usage thereof. SOLUTION: An organic field-effect transistor type gas sensor 3 includes a field-effect transistor 1 with an organic semiconductor layer and a temperature control mechanism 24 for controlling temperature of the field-effect transistor 1. COPYRIGHT: (C)2013,JPO&INPIT