A cooler for a semiconductor-module includes: a heat sink which has an appearance of a cuboid structure to one side of which a flow rate control plate is fixed; a thermal radiation plate on an outer surface of which semiconductor devices are bonded; and a tray-shaped cooling jacket having: a coolant introduction channel; a coolant extraction channel extending in parallel to the coolant introduction channel; and a cooling channel provided between the coolant introduction and extraction channels. The heat sink is provided in the cooling channel of the cooling jacket so that the flow rate control plate extends in a boundary between the coolant extraction channel and the cooling channel, and channels provided for the heat sink extend orthogonally to the coolant introduction and extraction channels. The thermal radiation plate is fixed so as to close an opening the cooling jacket.