Gas tungsten arc welding (GTAW) with three different heat inputs controlled by the weaving width was performed to understand their effects on the microstructural changes and pitting corrosion resistance during bead-on-pipe welding of super duplex stainless steel. The microstructure of the weld metals was categorized into three different types of zones: non-reheated, reheated type, and Retained Liquid zone. Even though single-pass welding with different weaving widths was employed, a reheated microstructure was detected, which has been previously observed with multiple pass welding. This phenomenon was called “dynamic reheating”, because it was produced by the weaving operation during welding regardless of the weaving width. The categorized area fraction varied with the weaving width change. Electron backscatter diffraction (EBSD) results at the side (the area near the fusion line) of the low-heat-input condition indicated a higher austenite volume fraction and a lower Cr2N fraction than that of the medium heat input condition. Thus, it described an inverse relationship, because higher heat input provided a higher austenite fraction. In addition, it was observed clearly that the austenite fraction at the medium heat input condition was dramatically increased by reheating, while the Cr2N fraction was reduced. Regardless of the weaving width, reheating contributed to the increase of the austenite fraction, further reducing the Cr2N quantity. The side areas in the map showed an inverse relationship in the reheated area fraction between low heat input and medium heat input. For this reason, the austenite fraction on the weld metal was determined not only by the heat input, but also by the amount of reheating. TEM analysis revealed that Cr2N in the non-reheated area was dispersed following heating and transformed to secondary austenite. Moreover, the pitting initiation and propagation relationship test with medium heat input condition presented that several pittings were initiated randomly regardless preference location and phases. However, pitting was propagated thorough ferrite phase dominant area, remaining austenite phase.