Size reduction of a power conversion device is intended. A power conversion device according to the present invention includes: a first power semiconductor module; a second semiconductor module; and a fixing member which fixes the first power semiconductor module, wherein the first power semiconductor module has a first power semiconductor device, a first case which houses the first power semiconductor device, and a first flange portion connected to the case, the second power semiconductor module has a second power semiconductor device, and a second case which houses the second power semiconductor device, the second case is connected to the first flange portion so as to provide a first flow path space for allowing a coolant to flow between the second case and the first case, and the first flange portion is fixed to the fixing member while supporting the first case and the second power semiconductor module.