A micro cooling fan includes a housing, a fan wheel, and a main circuit board. The main circuit board has a stator and a driving circuit. The stator is electrically connected to the driving circuit. The stator is disposed on a first inner surface, and the driving circuit is disposed on a first outer surface, so that the housing and the driving circuit of the micro fan motor form an integral structure. The first outer surface is opposite to the first inner surface, or the first outer surface is located on a side surface of the housing. Therefore, by disposing the driving circuit on the first outer surface, the wind resistance of the fan blades is reduced, and the air volume of the micro cooling fan is increased accordingly, so that the cooling effect of the micro cooling fan is improved.