An eccentric seat of an automobile grinding machine has a base, a grinding device, and a linking-fixing unit. The base has a base hole formed in the base. The grinding device is mounted in the base and has a grinding head. The grinding head has a head hole aligned with the base hole. The linking-fixing unit is mounted in the base hole and can move along the axial direction of the base hole and can be engaged the base. The linking-fixing unit has an inserting end that can be engaged in the head hole. When the inserting end is inserted into the head hole, the grinding head is fixed relative to the base, such that it is easy for the grinding head to combine with a grinding body, and the eccentric seat is suitable for polishing a surface of an automobile.