An inside of a housing of a power conversion device is partitioned by partitioning walls, and the power conversion device is configured from: an open part, into which external air flows; a first airtight part that is adjacent to the open part and into which no external air flows; and a second airtight part that is adjacent to the first airtight part and into which external air does not flow. At least two ventilation holes are formed in a partition wall between the first airtight part and the second airtight part. A circulation fan is provided to at least one of the at least two ventilation holes. The outer surface of the first airtight part is provided with a heatsink that dissipates heat transferred from an electronic component placed in the first airtight part, the heatsink being exposed to the open part.