A chemical interaction between an atmospheric pressure plasma jet and liquid media is of great interest for biomedical applications. In this paper, the visualization method and typical results of the 2-D distribution of oxidizing substances generated by the plasma jet were reported using the gel visualization reagent. The plasma jet generator consists of a glass tube and two electrodes. As a result, the distribution of oxidizing substances was able to be visualized around the contact point between the plasma jet and the reagent in atmospheric air. The interesting distribution patterns depending on the supplied gas were visually obtained by the reagent. In addition, its relative concentration distribution was also obtained by an absorbance measurement.