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 . <EOS>