A mobile work robot includes a running unit for movement, a working unit, a control unit controlling various portions of the mobile work robot with a provided instruction signal, an operation switch unit externally operated to provide the instruction signal for controlling an operation of the mobile work robot to the control unit; and a main battery supplying an electric power to the various portions of the mobile work robot. The control unit does not accept the provided instruction signal during the charging state when it is detected from a signal of a power supply connector that an AC adapter of the main battery is connected to achieve the charging state.