A charging apparatus for charging a battery for an electric power tool, the charging apparatus comprising: a control unit adapted to obtain information indicating a status of the battery from the battery and to control permitting or prohibiting charging the battery depending on whether or not the obtained information satisfies a predetermined first condition; a charging detecting unit (20, 22) adapted to detect whether or not the battery is being charged; a charging discontinuing unit adapted to obtain the information indicating the status of the battery from the battery and adapted to discontinue charging the battery independently of the control by the control unit to permit or prohibit charging when the obtained information satisfies a predetermined second condition; characterized in a diagnosing unit adapted to input diagnostic information satisfying the second condition to the charging discontinuing unit in addition to the information indicating the status of the battery or as a replacement for the information indicating the status of the battery based upon information entered from the control unit, wherein the control unit is adapted to perform a self-diagnostic process in which the control unit discontinues charging the battery via the charging discontinuing unit by outputting the diagnostic information satisfying the second condition to the diagnosing unit while permitting charging the battery, subsequently the control unit obtains from the charging detecting unit whether or not the battery is being charged, and the control unit initiates charging the battery by stopping outputting the diagnostic information satisfying the second condition to the diagnosing unit when the battery is not being charged and prohibits charging the battery when the battery is being charged. a control unit adapted to obtain information indicating a status of the battery from the battery and to control permitting or prohibiting charging the battery depending on whether or not the obtained information satisfies a predetermined first condition; a charging detecting unit (20, 22) adapted to detect whether or not the battery is being charged; a charging discontinuing unit adapted to obtain the information indicating the status of the battery from the battery and adapted to discontinue charging the battery independently of the control by the control unit to permit or prohibit charging when the obtained information satisfies a predetermined second condition; characterized in a diagnosing unit adapted to input diagnostic information satisfying the second condition to the charging discontinuing unit in addition to the information indicating the status of the battery or as a replacement for the information indicating the status of the battery based upon information entered from the control unit, wherein the control unit is adapted to perform a self-diagnostic process in which the control unit discontinues charging the battery via the charging discontinuing unit by outputting the diagnostic information satisfying the second condition to the diagnosing unit while permitting charging the battery, subsequently the control unit obtains from the charging detecting unit whether or not the battery is being charged, and the control unit initiates charging the battery by stopping outputting the diagnostic information satisfying the second condition to the diagnosing unit when the battery is not being charged and prohibits charging the battery when the battery is being charged.