[Problem] To provide a vehicular arm component which is easily manufactured and advantageous in reducing a cost without causing a steep change in a cross section.[Solution] A vehicular arm component is formed by subjecting a workpiece (W), the workpiece being a flat plate extending in a plane formed by a first direction and a second direction orthogonal to the first direction, to press processing in stages so as to butt and joint two side surfaces in the second direction. The vehicular arm component includes: a cylindrical portion (10) configured to be provided along the first direction and have a cylindrical shape; a bracket portion (20) configured to be provided in either end in the first direction of the cylindrical portion and have an outer diameter expanding as it goes to the outside in the first direction; and two flange portions (30) configured to be provided to face each other along the second direction in the bracket portion and provided with through holes (20H) at positions facing each other along the second direction.