Method for producing vanadium compound, method for producing vanadium solution, and method for producing redox flow battery electrolytic solution

This method for producing a vanadium compound comprises: an alkali leaching step for obtaining a leachate slurry by immersing incineration ash in an alkaline solution to leach vanadium from the incineration ash into the alkaline solution; a solid-liquid separation step for obtaining a leachate by subjecting the leachate slurry obtained in the alkali leaching step to solid-liquid separation to remove insoluble matter; a pH adjustment step for adding an acid to the leachate after the solid-liquid separation so as to acidify the leachate; an aging step for aging the leachate after the pH adjustment until a precipitate precipitates out of the leachate; and a separation step for separating the precipitate from the leachate after the aging step.