An automobile undercarriage part comprising: a welded joint in which a first steel sheet and a second steel sheet each having a tensile strength of 780 MPa or higher are overlapped and a fillet weld is formed between an end surface of the first steel sheet and a surface of the second steel sheet, wherein a chemical composition of a weld metal that forms the welded joint 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%; S: more than 0% to 0.030%; Cu: 0% to 0.50%; Cr: 0% to 1.5%; Nb: 0% to 0.3%; V: 0% to 0.3%; Mo: 0% to 1.0%; Ni: 0% to 2.5%; B: 0% to 0.005%; and a remainder consisting of iron and impurities, the following formula , formula , formula , and formula are satisfied, and slag in a toe portion of the fillet weld satisfies the formula , Al + Ti > 0.05 Ti / Al > 0.9 7 × Si + 7 × Mn − 112 × Ti − 30 × Al ≤ 12 2.0 < Si + Mn Ti content on slag surface > Si content on slag surface where [Si], [Al], [Ti], and [Mn] mean an amount of each component by mass% with respect to the total mass of the weld metal, wherein an upper limit of [Al] + [Ti] is 0.60, and the chemical composition of the weld metal, the Ti content on slag surface and the Si content on slag surface are measured as described in the description. a welded joint in which a first steel sheet and a second steel sheet each having a tensile strength of 780 MPa or higher are overlapped and a fillet weld is formed between an end surface of the first steel sheet and a surface of the second steel sheet, wherein a chemical composition of a weld metal that forms the welded joint 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%; S: more than 0% to 0.030%; Cu: 0% to 0.50%; Cr: 0% to 1.5%; Nb: 0% to 0.3%; V: 0% to 0.3%; Mo: 0% to 1.0%; Ni: 0% to 2.5%; B: 0% to 0.005%; and a remainder consisting of iron and impurities, the following formula , formula , formula , and formula are satisfied, and slag in a toe portion of the fillet weld satisfies the formula , Al + Ti > 0.05 Ti / Al > 0.9 7 × Si + 7 × Mn − 112 × Ti − 30 × Al ≤ 12 2.0 < Si + Mn Ti content on slag surface > Si content on slag surface where [Si], [Al], [Ti], and [Mn] mean an amount of each component by mass% with respect to the total mass of the weld metal, wherein an upper limit of [Al] + [Ti] is 0.60, and the chemical composition of the weld metal, the Ti content on slag surface and the Si content on slag surface are measured as described in the description. 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%; S: more than 0% to 0.030%; Cu: 0% to 0.50%; Cr: 0% to 1.5%; Nb: 0% to 0.3%; V: 0% to 0.3%; Mo: 0% to 1.0%; Ni: 0% to 2.5%; B: 0% to 0.005%; and a remainder consisting of iron and impurities, the following formula , formula , formula , and formula are satisfied, and slag in a toe portion of the fillet weld satisfies the formula , Al + Ti > 0.05 Ti / Al > 0.9 7 × Si + 7 × Mn − 112 × Ti − 30 × Al ≤ 12 2.0 < Si + Mn Ti content on slag surface > Si content on slag surface where [Si], [Al], [Ti], and [Mn] mean an amount of each component by mass% with respect to the total mass of the weld metal, wherein an upper limit of [Al] + [Ti] is 0.60, and the chemical composition of the weld metal, the Ti content on slag surface and the Si content on slag surface are measured as described in the description. <EOS>