A power transmission device includes: a main case having an inside storing an oil; a drum carrying up the oil; and a partition wall partitioning the inside of the main case into a transmission gear housing containing the drum and a catch tank. An inner wall of the main case includes a down-extending portion extending down toward a feed opening of the catch tank, and extending toward the drum rather than along a vertical plane extending in the vertical direction as the down-extending portion extends downward, and a receding portion bordering on the down-extending portion and extending away from the drum from a bordering point where the receding portion borders on the down-extending portion.