In this paper, we report on our attempt to make a thin film of Zn3P2 compound semiconductor by electrodeposition from aqueous solutions containing zinc and phosphorus species. First of all, we constructed the potential-pH diagram of the Zn-P-H2O system at 363 K and found out the wide stable region of Zn3P2 at lower potentials. In the cyclic voltammetry on SnO2 glass substrate, two cathodic current changes and an anodic peak were observed. This is similar results to Soliman et al., where the electrodeposition of Zn3P2 was succeeded. Consequently, the potentiostatic electrolysis thus was carried out to clarify the reduced substance and the reduction of SnO2 was only observed. When Au electrode was used as an inert electrode, the formation of Zn3P2 was not also observed, while the Au-Zn compound was confirmed. It is considered that the precipitation of zinc predominantly occurs and the reduction of phosphate ions are kinetically difficult from the results of the cyclic voltammetry. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.003204jes] All rights reserved.