A drive device includes a rotating electrical machine; a planetary gear unit positioned radially inside the rotating electrical machine so as to axially overlap the rotating electrical machine; a through shaft extending radially inside and through a sun gear of the planetary gear unit; and a case that accommodates the rotating electrical machine and the planetary gear unit. The through shaft is supported by the case on both axial sides of the planetary gear unit, and a rotor of the rotating electrical machine is connected integrally with the sun gear and is rotatably supported at two axial positions, the rotor is supported at a first axial position of the two axial positions by the case, and the rotor is supported at a second axial position of the two axial positions at a position radially inside the sun gear by the through shaft.