A drive device includes a shaft rotatably supported by a first bearing and a second bearing. The first bearing is disposed in a shaft hole of an output frame end. The second bearing is disposed in a bearing box of an opposite-to-output frame end. An oil seal is fixed in the shaft hole and is closer to an output end than the first bearing is, and is in sliding contact with an outer circumference of the shaft. A biasing member is housed in the bearing box and biases an outer race of the second bearing toward the output end. Accordingly, a deflection amount and a bend amount of the shaft at the location where the oil seal is disposed may be reduced.