Potential barriers and their contribution have been visualized in an organic field-effect transistor composed of copper-phthalocyanine (CuPc) thin film via scanning gate microscopy (SGM). The SGM response shows a peak when a biased tip situates on both edges of the Au electrode at the lower source-drain voltages. It indicates that the electric field from the tip modulates the Schottky-type potential barrier at the CuPc/Au interface and the barriers strongly restrict the carrier (hole) injection and/or emission at the CuPC channel. On the other hand, a significant peak appears only at the source (hole-injection) side at higher bias voltages. The difference indicates that the contribution of the barrier to the transport changes with the bias condition. The electrostatic force microscopy response, which is simultaneously obtained with the SGM image, Supports these considerations. Moreover, it is confirmed that the peak height is related to the distribution of current injection into the channel. (C) 2009 American Vacuum Society. [DOI: 10.1116/1.3013853]