A power conversion device comprising: a capacitor which smoothes DC current; power semiconductor modules (300U - 300W) in each of which power semiconductor devices for converting the DC current into AC current are stored in a module case in a bottomed tubular shape and DC terminals, an AC terminal and signal terminals (325U, 336U, 325L, 336L) are extracted from an extracting part of the module case; a capacitor bus bar which connects the capacitor with the DC terminals; a first channel body in which a first coolant channel is formed to allow the power semiconductor modules to be inserted therein; a second channel body in which a second coolant channel for cooling the capacitor and the capacitor bus bar is formed; and a housing having a base on which the first and second channel bodies (12A, 12B) are arranged in parallel, wherein a prescribed space is formed between the coolant channel bodies (12A, 12B), and openings (100A, 100B, 100C) formed in areas of the base facing the prescribed space, wherein: the power semiconductor modules (300U - 300W) are inserted into the first coolant channel so that the extracting parts of the module cases are arranged at the face of the first channel body facing the prescribed space, and the capacitor bus bar is extracted from the second channel body to the prescribed space, and the DC terminals are connected with the capacitor bus bar at positions facing the openings (100A, 100B, 100C). a capacitor which smoothes DC current; power semiconductor modules (300U - 300W) in each of which power semiconductor devices for converting the DC current into AC current are stored in a module case in a bottomed tubular shape and DC terminals, an AC terminal and signal terminals (325U, 336U, 325L, 336L) are extracted from an extracting part of the module case; a capacitor bus bar which connects the capacitor with the DC terminals; a first channel body in which a first coolant channel is formed to allow the power semiconductor modules to be inserted therein; a second channel body in which a second coolant channel for cooling the capacitor and the capacitor bus bar is formed; and a housing having a base on which the first and second channel bodies (12A, 12B) are arranged in parallel, wherein a prescribed space is formed between the coolant channel bodies (12A, 12B), and openings (100A, 100B, 100C) formed in areas of the base facing the prescribed space, wherein: the power semiconductor modules (300U - 300W) are inserted into the first coolant channel so that the extracting parts of the module cases are arranged at the face of the first channel body facing the prescribed space, and the capacitor bus bar is extracted from the second channel body to the prescribed space, and the DC terminals are connected with the capacitor bus bar at positions facing the openings (100A, 100B, 100C). the power semiconductor modules (300U - 300W) are inserted into the first coolant channel so that the extracting parts of the module cases are arranged at the face of the first channel body facing the prescribed space, and the capacitor bus bar is extracted from the second channel body to the prescribed space, and the DC terminals are connected with the capacitor bus bar at positions facing the openings (100A, 100B, 100C).