An exhaust gas processing device includes a NOx detection sensor, a first catalyst provided to a first branch pipe, a second catalyst provided to a second branch pipe, a first pressure sensor and a second pressure sensor which are arranged on the upstream side of the first catalyst and the second catalyst and which detect pressures in the first branch pipe and the second branch pipe, and a control device that obtains flow rates of exhaust gas flowing through the first branch pipe and the second branch pipe based on detection values of the first pressure sensor and the second pressure sensor and obtains amounts of reducing agent to be given to the first catalyst and the second catalyst from the obtained flow rates and a concentration of NOx of the exhaust gas.