When the fluorescence of a material under transparent conductive films is measured, it is sometimes required that the transparent conductive films have low fluorescence intensity to prevent stray light. Herein, the oxygen partial pressure during sputtering is varied and the transmittance, resistivity, and fluorescence intensity are measured to clarify the cause of the fluorescence of indium tin oxide (ITO) and In2O3. The fluorescence intensity of both ITO and In2O3 decreases with an increase in the oxygen partial pressure in the case of as‐deposited films. The cause of fluorescence is considered to be oxygen vacancies. ITO can maintain low resistivity even with a small amount of oxygen vacancies since it contains SnO2, which generates carriers. High‐temperature annealing also introduces other defects, which increases the fluorescence intensity.