This operation management device is provided with: a state acquisition unit that acquires the measurement value of a first state quantity indicating the operation state of a power generation plant; a state update unit that updates, on the basis of the measurement value of the first state quantity, the estimate value of a second state quantity indicating the operation state of the power generation plant, said second state quantity being a state quantity different from the first state quantity; and a management unit that manages, on the basis of the estimate value of the second state quantity, the operation state of the power generation plant.