The invention discloses a micro direct current motor which comprises a motor housing, a stator assembly and a rotor assembly. The stator assembly and the rotor assembly are arranged in the motor housing. The rotor assembly comprises an impeller and an impeller rotation shaft. The exterior surface of the rotation shaft is provided with two annular first rolling ball grooves at interval. The exterior part of the rotation shaft is sleeved by an installation sleeve that surrounds the two annular first rolling ball grooves. The inner wall of the installation sleeve is provided with two corresponding second rolling ball grooves at interval. A plurality of rolling balls is placed between the first rolling ball grooves and the second rolling ball grooves. The micro direct current motor of the invention does not utilize bearings as the rotation connection components, exempt from the jolting and shaking of the rotation shaft due to the gaps formed during the assembling of the outer rings and the inner rings of bearings and rolling balls. At the same time, the springs between two bearings can be saved. Therefore, the assembled structure is a simplified one. And even at a high speed, the rotation shaft runs stably without producing sounds.