Provided is a method of fabricating an organic thin film transistor (OTFT) using surface energy control. The method changes a polarity of a gate insulating layer to a polarity of a semiconductor channel layer to be formed on the gate insulating layer by controlling surface energy of the gate insulating layer, thereby promoting growth of the semiconductor channel layer on the gate insulating layer. According to the method, the interface characteristics between the gate insulating layer and the semiconductor channel layer are improved, and thus it is possible to implement an OTFT that can minimize leakage current and has high field effect mobility and low turn-on voltage.