An apparatus for hanging on seatback inside vehicle is provided, including a support unit, a platform unit, a fasten unit and a push unit. The support unit and the platform unit are coupled on one side, and can be expanded to an L shape structure. The platform unit includes a first placement area and at least a concave positioning groove on the side facing the support unit. The platform unit includes a hanger shoulder. The support unit is disposed with a press element able to adjust position on side wall facing the platform unit. The fasten unit is coupled to back of the support unit for fastening to column of seat headrest. The push unit is installed at the platform unit, and can extend beyond the platform unit after adjustment. As such, the apparatus allows the backseat passenger to use portable electronic device or hanging clothes.