Power conversion sub-blocks (75a and 75b) are combined to be configured as a power conversion block 70a. The power conversion sub-blocks (75a and 75b) include power conversion modules including cooler base sections (27a to 27d) on which semiconductor elements 25 are mounted and cooler fin sections (26a to 26d) provided on the rear surface side of semiconductor element mounting surfaces in the cooler base sections (27a to 27d) and cooler attachment member (72a and 72b) to which the cooler fin sections (26a and 26b) and cooler fin sections (26c and 26d) are attached back to back, the cooler attachment members (72a and 72b) being configured to be capable of separating an opened section where the cooler fin sections (26a and 26b and 26c and 26d) are present and external air circulates and a closed section where the semiconductor elements are present and circulating cooling air to the cooler fin section (26a to 26d).
