To provide a knuckle structure of an automobile which can improve sensing performance (improvement of ABS performance) of an ABS sensor by reducing inclination of an ABS sensor fitting boss, reduce the weight of a knuckle and improve strength and rigidity balance of a tie rod arm and the ABS sensor fitting boss.

In this knuckle structure of an automobile in which the tie rod arm 2b to which a tie rod 6 is connected through a ball stud 8 is integrally formed on the knuckle 2, and the ABS sensor fitting boss 9 is integrally formed don the knuckle 2 adjacent to the base end of the tie rod arm 2b, in an area of the tie rod arm 2b extending from the base end part (root part) of the ABS sensor fitting boss 9 to a tip portion 9a, the car body inner part and the car body outer part of a tie rod arm base part 10 are formed like a straight line.