A microchannel heat exchanger is a heat exchanger for cooling hydrogen gas with a cooling medium, and includes a cooling side layer formed with a plurality of medium flow paths for flowing the cooling medium, and a high temperature side layer formed with a plurality of hydrogen flow paths for flowing the hydrogen gas and a first introduction port for flowing the hydrogen gas into the plurality of hydrogen flow paths. The first introduction port has a circular shape or an elliptical shape. An inflow end of each of the plurality of hydrogen flow paths is connected to a peripheral surface of the first introduction port. The hydrogen flow path extends from the first introduction port to the first lead out port without branching.