The effect of oxygen doping on titanyl phthalocyanine (TiOPc) films was investigated by ultraviolet photoelectron spectroscopy (UPS). The energy of the electronic levels of TiOPc films probed by UPS was clearly different between the film deposited in ultrahigh vacuum (UHV) and in O-2 atmosphere. The film deposited in UHV showed downward band bending characteristic of n-type semiconductor. On the other hand, the film deposited under O-2 atmosphere showed upward band bending characteristic of p-type semiconductor. Such trends are in excellent correspondence with reported field effect transistor characteristics.