To solve a problem that a shielding gas saving effect obtained by introducing a gas flow rate controlling means can not be easily grasped.

In the arc welding equipment 1, shielding gas output is started or stopped by a mass flow controller 31. A robot controller 16 measures a gas ON elapsed time from output to stop of a shielding gas and a gas OFF interval time from stop to start of the shielding gas; in accordance with the measured gas OFF interval time, one table is selected from a plurality of gas saving amount characteristic tables in which relationships between the gas ON elapsed time and the gas saving amount are determined; a saving amount per output of the shielding gas is calculated by inputting the gas ON elapsed time into the gas saving amount characteristic table; and a saving effect value in which the gas saving amount is integrated is calculated and displayed on a teach pendant 15. Thus, the shielding gas saving effect obtained by introducing the gas flow rate controlling means can be easily grasped without using a special measuring instrument.