A semiconductor unit may include first coolers arranged in parallel; semiconductor modules, each of the semiconductor modules being interposed between a pair of the first coolers arranged adjacently; a coolant discharge pipe provided at one of the first coolers that is located at an end of a stack of the first coolers and the semiconductor modules, the coolant discharge pipe extending along a stacking direction of the first coolers and the semiconductor modules; a second cooler connected with the coolant discharge pipe; and a reactor interposed between the second cooler and the one of the first coolers located at the end of the stack.