A semiconductor device may include coolers, semiconductor modules, and a pair of connecting pipes. The coolers are arranged in a line and each of which includes a first flow path. Each of the semiconductor modules is interposed between a corresponding pair of the coolers. Each of the connecting pipes communicates with the adjacent coolers. A pair of coolant holes may be provided at one of the coolers located at one end in the stacking direction. A pair of second flow paths may extend respectively from the coolant holes to one of the coolers located at other end in the stacking direction. A bolt-head retainer and an internally threaded portion may be provided in each second flow path, the bolt-head retainer retaining a head of a bolt, and the internally threaded portion fixing the bolt. The coolers between the bolt-lead retainers and the internally threaded portions are fixed by the bolts.