PURPOSE: To make setting of a welding condition easy and to perform optimum welding in the stage of welding with a robot by storing many welding conditions and making the prescribed welding condition selectable among said conditions.

CONSTITUTION: Welding conditions such as welding voltage, welding current, preflow time, post flow time, crater treatment time, or the like are stored in a memory in the stage of impressing a voltage between a wire and a welding member, and welding the part to be welded by a robot while delivering off successively the wire. The prescribed welding condition is specified by a program and said condition is read out from a memory. A welding machine is controlled by such welding condition, whereby welding is performed. The operation for determining the optimum welding condition, etc. are made easy and the optimum welding is performed by the above-mentioned method.