There is provided a motor controller that can easily reduce the size and manufacturing cost of a motor controller by reducing the size of a heat sink without increasing the number of parts much.The motor controller includes a heat sink, a plurality of power semiconductor modules that is in close contact with the heat sink, a substrate (6) that is electrically connected to the plurality of power semiconductor modules, and a fan (8) that generates the flow of external air and supplies cooling air to the heat sink. The heat sink is formed by the combination of two kinds of heat sinks that include a first heat sink (9) and a second heat sink (10), and at least one of the power semiconductor modules is in close contact with each of the first and second heat sinks (9) and (10).