We demonstrated an ambipolar-type organic field-effect transistor (OFET) in a dual-gate configuration where two different layers of unipolar organic semiconductors (OSC) are stacked. In our OFET, the hole-channel for the p-type operation depends primarily on the corresponding gate insulator-OSC interface and the electron-channel for the n-type operation on the remaining interface in an independent manner. Using a combination of two independent gate voltages, the charge transport can be efficiently controlled and the on-off current ratio becomes enhanced in a dual-gate configuration. The optimization of the materials, the interfaces, and the device architectures will lead to a wide range of organic electronic applications.