In semi-automatic arc welding, the set voltage (arc length) conditions are kept almost constant. However, the current condition changes depending on the wire protrusion length due to the movement of the hand during work. In addition, changing the torch holding angle during welding also changes the wire protrusion length and the current. Therefore, it is necessary to understand the mechanism by which the welding results such as penetration change due to these changes in semi-automatic arc welding. By using this system, welding work can be performed while checking the change in the current value due to the change in the wire protrusion length, which is effective for technical verification and guidance.