In the welded joints, it becomes a common idea that the strength of weld metal is equal to or higher than it of base metal from the viewpoints of efficiency of welded joints. Otherwise, it is effective to use the weld metal whose strength is lower than it of base metal in order to prevent the initiation of weld cracking. In this report, the static tensile behaviors of the welded joints having weld metal whose strength is lower than it of base metal --so called “Soft Welded Joints” --are investigated. The “all soft welded joint” in which all weld metal are soften metal and the “partial soft welded joint” in which only a part of weld metal is soften metal were made by metal-arc welding. The main results obtained are summarized as follows : (1) The strength of the welded joints using soft weld metal whose strength is lower than it of base metal is much elevated from it of the soft weld metal itself. It is effective to use soft weld metal in a part of weld metal from the viewpoint of efficiency of strength. (2) The two standard strengths are considered as the required strength σ _u of welded joint, or (i) σ _u ≥σ _u ^B (ii) σ _u ≥ (guaranteed strength for design). The “Soft Ratio” S_r of weld metal required to guarantee the standard strength and the elongation of welded joints are considered (Table 6). When S_r (=σ _u ^W /σ _u ^B ) ≥0.93, ultimate tensile strength and elongation of all kinds of soft welded joints become almost equal to those of base metal.