Abstract: A positioning device of vehicle roof rack of the present invention includes a base, a positioning element, a buckle element, and a fixing element. The base forms a plurality of positioning slots and a connecting slot connecting the positioning slots. The positioning element is disposed slidably on the connecting slot and is able to be received in one of the positioning slots alternatively. An end of the buckle element is fixed to the positioning element by the fixing element, and the other end of the buckle element is to be buckled to a perimeter edge of a vehicle. Thereby, the position the buckle element being buckled to the perimeter edge can be adjusted by moving the positioning element. Thus, the positioning device of vehicle roof rack can be employed on vehicles in different sizes.