A solar fail-safe device according to an embodiment of the present disclosure is capable of operating a valve by using sunlight and operating the valve in an emergency in which electricity is not supplied to an actuator unit moving the valve. A solar fail-safe device may include a solar panel module producing electricity from solar energy, an actuator unit including an actuator moving a valve by using electricity as a power source, and a fail-safe part moving the valve by using emergency electricity with which the fail-safe part is pre-charged, and a control unit receiving the electricity produced from the solar panel module to charge a first and a second battery and to supply the electricity to the actuator unit. The actuator may move the valve by using the emergency electricity when a voltage at which the electricity is applied from the control unit is less than a predetermined value.