The invention provides a method of recovering a copper component or a manganese component from a cleaning agent containing copper oxide, a cleaning agent containing basic copper carbonate, a cleaning agent containing copper hydroxide, or a cleaning agent containing copper oxide and manganese oxide, the cleaning agents having been used for removing, through contact with a harmful gas, a phosphine contained as a harmful component in the harmful gas. Also, the invention provides a method of recovering a copper component or a manganese component from a cleaning agent containing basic copper carbonate, a cleaning agent containing copper hydroxide, or a cleaning agent containing copper oxide and manganese oxide, the cleaning agents having been used for removing, through contact with a harmful gas, a phosphine contained as a harmful component in the harmful gas. According to the present invention, the copper component and/or the manganese component can be effectively recovered from the cleaning agents in a recyclable form.