A power conversion device that includes a power convertor for converting an input power to output the converted power, and a controller for controlling an electronic component included in the power convertor, the power conversion device comprising: an open part allowing inflow of external air into the open part, the external air being air from outside of the power conversion device; a first airtight part adjacent to the open part, the first airtight part containing the electronic component and being sealed to be free from inflow of the external air into the first airtight part; a second airtight part adjacent to the first airtight part, the second airtight part containing the controller and being sealed to be free from inflow of the external air into the second airtight part, at least two ventilation holes being formed in a partition wall between the first airtight part and the second airtight part; a heatsink that is placed in a housing forming the first airtight part and that is configured to release to outside of the power conversion device, at least some of heat transferred from the electronic component placed in the first airtight part; and a circulation fan that is provided in at least one of the ventilation holes, characterized in that the power conversion device further comprises: a reactor connected to an input side of the power convertor, the open part containing the reactor, a circulation fan controller configured to regulate an amount of airflow blown by the circulation fan in accordance with a temperature difference between the first airtight part and the second airtight part. an open part allowing inflow of external air into the open part, the external air being air from outside of the power conversion device; a first airtight part adjacent to the open part, the first airtight part containing the electronic component and being sealed to be free from inflow of the external air into the first airtight part; a second airtight part adjacent to the first airtight part, the second airtight part containing the controller and being sealed to be free from inflow of the external air into the second airtight part, at least two ventilation holes being formed in a partition wall between the first airtight part and the second airtight part; a heatsink that is placed in a housing forming the first airtight part and that is configured to release to outside of the power conversion device, at least some of heat transferred from the electronic component placed in the first airtight part; and a circulation fan that is provided in at least one of the ventilation holes, characterized in that the power conversion device further comprises: a reactor connected to an input side of the power convertor, the open part containing the reactor, a circulation fan controller configured to regulate an amount of airflow blown by the circulation fan in accordance with a temperature difference between the first airtight part and the second airtight part. a reactor connected to an input side of the power convertor, the open part containing the reactor, a circulation fan controller configured to regulate an amount of airflow blown by the circulation fan in accordance with a temperature difference between the first airtight part and the second airtight part.