One of the important factors of cell performance in polymer electrolyte fuel cell (PEFC) is moisture control in gas diffusion layer (GDL). It is necessary to clarify the mass transfer characteristics in GDL. The oxygen diffusion coefficient in GDL is measured with a galvanic battery type oxygen absorber. Particularly, measurement in high accuracy of oxygen diffusion coefficient in GDL becomes important. In the previous study, the measurement of the effective oxygen diffusivity in the microporous GDL using the galvanic cell type oxygen absorber was proposed. In addition, the measurement of the effective oxygen diffusivity in the microporous GDL containing moisture was proposed and shown to be an effective technique for measurement of the effective oxygen diffusivity in microporous media. However, because the diffusion resistance of dry GDL is small, the error margin of tens of percent existed in the result of a measurement of the oxygen diffusivity. In the present study, the objective of this study is high precision measurement of the oxygen diffusion coefficient in GDL by specifying the error factors and improving them.