Abstract: In one embodiment, a steam turbine plant includes a first turbine driven by steam from a boiler, a second turbine driven by steam from a reheater, a third turbine driven by the steam exhausted from the second turbine, and a carbon dioxide capturing system including a reboiler to heat an absorbing liquid with the steam exhausted or extracted from the second turbine. The plant further includes a steam pipe to feed the steam exhausted from the second turbine to the third turbine, and a first steam extraction pipe to send the steam exhausted or extracted from the second turbine to the reboiler. The plant further includes a pressure detector to detect a pressure of the steam flowing through the steam pipe or the first steam extraction pipe, a pressure adjustment valve provided on the steam pipe, and a controller to control the valve based on the detected pressure.