The utility model discloses an oil supply device of a diesel engine and relates to the technical field of the oil supply device. The oil supply device of the diesel engine comprises a bottom tank and an overhead tank, and is characterized in that a via hole is arranged at the middle portion of a side plate of a pump chamber of the bottom tank, a connecting pin roll which is matched with the via hole is arranged in the via hole, a lower positioning plate is arranged on the upper edge of the side plate, and an upper positioning plate is fixedly connected with the outer side of the overhead tank. On the basis of that used space and transport space are not increased in the oil supply device of the diesel engine, use and transportation of the overhead tank is achieved, and the overhead tank is not required to be rotated when in use so as to improve safety coefficient of use of the overhead tank. In addition, the oil supply device of the diesel engine is simple in structure and low in manufacturing cost. The oil supply device of the diesel engine also has good prospect of popularization and use.