To improve efficiency in overall energy utilization of a cogeneration plant, to make compact downstream appliances further downstream than a prime mover such as an exhaust heat collecting boiler and an exhaust heat collecting boiler outlet duct, and to shorten the starting time of the system and improve operability.

The cogeneration plant is for: leading exhaust gas from the prime mover 3 to the exhaust heat collecting boiler 6; generating steam by collecting heat of exhaust gas in the exhaust heat collecting boiler 6 and generating electricity by driving a generator by output of rotary shaft of a steam turbine 10 by leading the steam to the steam turbine 10 and driving the steam turbine 10; and releasing a part of the steam and supplying the rest to other facilities. The cogeneration plant is characterized in having arranged an induced draft fan 15 for inducing exhaust gas into an outlet exhaust gas passage 14 of the exhaust heat collecting boiler 6, and having a structure for utilizing entire driving force or a part of it of the rotary shaft of the steam turbine 10 as a driving source of the rotary shaft of the induced draft fan 15.