A power conversion device comprising: a power conversion unit (70, 80) to convert an input power and output the converted power; a reactor connected to an input side of the power conversion unit (70, 80); a controller to control electronic components included in the power conversion unit (70, 80); a first unit, an interior of a housing thereof being divided by a partition into a closed section into which outside air does not flow and an open section into which the outside air flows, the closed section containing the electronic components, the first unit comprising a heat sink exposed to the open section and releasing heat transferred from the electronic components; a second unit, an interior of a housing thereof being divided into a first space and a second space by a partition having an opening, the second unit being adjacent to the first unit, the second unit containing in the first space a blower for blowing air from the second space toward the first space, the blower having an impeller at least partially exposed to the second space from the opening; and a third unit adjacent to the second unit and containing the reactor, wherein a first vent is formed in a part at which a housing forming the open section contained within the first unit and a housing forming the second space contained within the second unit contact each other, a flow inlet into which the outside air flows is formed in the housing forming the open section contained within the first unit, a second vent is formed in a part at which a housing forming the first space contained within the second unit and a housing of the third unit contact each other, and a flow outlet is formed in the housing of the third unit and discharges air flowing in from the second vent, wherein the blower does not comprise a casing. a power conversion unit (70, 80) to convert an input power and output the converted power; a reactor connected to an input side of the power conversion unit (70, 80); a controller to control electronic components included in the power conversion unit (70, 80); a first unit, an interior of a housing thereof being divided by a partition into a closed section into which outside air does not flow and an open section into which the outside air flows, the closed section containing the electronic components, the first unit comprising a heat sink exposed to the open section and releasing heat transferred from the electronic components; a second unit, an interior of a housing thereof being divided into a first space and a second space by a partition having an opening, the second unit being adjacent to the first unit, the second unit containing in the first space a blower for blowing air from the second space toward the first space, the blower having an impeller at least partially exposed to the second space from the opening; and a third unit adjacent to the second unit and containing the reactor, wherein a first vent is formed in a part at which a housing forming the open section contained within the first unit and a housing forming the second space contained within the second unit contact each other, a flow inlet into which the outside air flows is formed in the housing forming the open section contained within the first unit, a second vent is formed in a part at which a housing forming the first space contained within the second unit and a housing of the third unit contact each other, and a flow outlet is formed in the housing of the third unit and discharges air flowing in from the second vent, wherein the blower does not comprise a casing.