A power conversion device includes a cooling structure capable of cooling down, by a coolant that flows through a first flow channel formed by a first wall portion and a second wall portion facing with each other, a first electronic component and a second electronic component mounted on an external surface of the first wall portion. The first wall portion is formed in a stepwise shape, and includes a first mount portion on which the first electronic component is mounted, a second mount portion which has a different height from the first mount portion, and on which the second electronic component is mounted, and a first connection portion that is extended between the first mount portion and the second mount portion.