To solve the problem that the displayed information in a conventional monitoring device for arc welding equipment is difficult to be, viewed and discriminated when the device is installed in a bright place.

The state of output and stop of an arc welding power supply are discriminated, so that a graphic shape and color arrangement are changed in relation to an arc welder in a monitoring software. In addition, the graphic shape is designed to match the tip shape of a welding torch. The monitoring device is equipped with an alarm function, which is activated if the welding output is in excess of a preset range. In connection with this function, the graphic shape for the alarm is changed respectively before and after the activation.