Steam supply system and CO2 recovery unit including the same

A steam supply system that can reheat CO2 absorbing liquid without lowering performance of a reboiler by decompressing a condensed water drum is provided. This system includes a reboiler that raises the temperature of absorbing liquid contacted with exhaust gas discharged from a boiler to absorb CO2 in the exhaust gas and heated to eliminate CO2. The reboiler includes a heat exchanger tube to which steam for heating is supplied and a condensed water drum that recovers condensed water of the steam introduced from the heat exchanger tube as steam drain, and the condensed water drum is provided with decompression unit that lowers pressure in the condensed water drum.