A heat exchanger 1 comprises a shell 2 which has in an interior thereof a heat exchange chamber 20 in which a gas to be cooled or an intermediate medium is filled, and performs heat exchange directly or indirectly between liquid hydrogen and the gas to be cooled, in the interior of the heat exchange chamber 20; a tray 23 which is provided in the interior of the heat exchange chamber 20 and receives a liquefied gas and a deposited substance F which are generated by the heat exchange in the interior of the heat exchange chamber 20; and a liquid discharge mechanism (flashboard 22, drain port 25, and drain pipe 26) which discharges the liquefied gas from the tray 23 in a state in which the deposited substance F is left in the tray 23.