GAS COOLER

A gas cooler includes a drain recovery part, a drain discharge flow path, a drain tank, and a ventilation flow path. In the drain recovery part, drain separated from gas is accumulated by cooling the gas in a cooling part. The drain tank includes a separation part in which the drain and the gas are separated, and a storage part in which the separated drain is stored. The drain discharge flow path has one end communicating with the drain recovery part and the other end communicating with the separation part. The ventilation flow path has one end communicating with the separation part, and the other end communicating with a gas flow path that leads to a downstream space above the drain recovery part and to a gas lead-out port.