A voltage at an output end of a switch of an electric vehicle supply equipment is detected before charging an electric vehicle. An earth leakage circuit breaker is tripped for cutting off power inputted to the switch and preventing the output end from outputting the power when the voltage is higher than a first predetermined value. The switch is turned on for outputting the power from the output end to charge the electric vehicle when the voltage is lower than the first predetermined value. A current is detected at the output end. Power inputted to the switch is cut off for preventing the output end from outputting the power when the current is higher than a second predetermined value.