An automobile undercarriage part of the present invention has a welded joint formed by base steel plate, wherein the chemical composition of a weld metal contains, with respect to a total mass of the weld metal, by mass %, C: 0.02% to 0.30%, Si: 0.10% to less than 1.0%, Mn: 1.2% to 3.0%, Al: 0.002% to 0.30%, Ti: 0.005% to 0.30%, P: more than 0% to 0.015%, and S: more than 0% to 0.030%, the following formula (1A), formula (1B), formula (2), and formula (3) are satisfied, and slag in a toe portion of the fillet weld satisfies a formula (4). [Al]+[Ti]>0.05  Formula (1A) [Ti]/[Al]>0.9  Formula(1B) 7×[Si]+7×[Mn]−112×[Ti]−30×[Al]≤12  Formula (2) 2.0 [Si content on slag surface]  Formula (4).