Abstract: Process for reclaiming stannous ion by reducing the same in an electrolyte to stannic ion through a simple operation in a short period of time, which comprises the steps of preparing the electrolyte in an acidic range as required and then adding metallic tin to the electrolyte and heating the mixture to at least 80.degree. C., in order to reduce the stannous ion oxidized in the electrolyte containing tin salt to obtain a stable electrolyte treated product. This process may be utilized particularly for effectively reducing and reclaiming an electrolyte which contains tin salt used for electrolytically coloring aluminum.