A fuel burning heater comprises a housing 1 provided with a fluid passage 13 defined in a wall thereof, and a burner 2 accommodated in an inside space of the housing 1 to heat fluid filled in the fluid passage 13. A fuel supply device 3 supplies fuel into the burner 2. An air supply device 4, including an air supply pipe 41, supplies air into the burner 2. An exhaust gas circulating device 5 circulates exhaust gas, produced in the burner 2 by combustion of air-fuel mixture, to the air supply pipe 41. A control unit 7 increases an amount of the exhaust gas circulated by the exhaust gas circulating device 5 when an amount of fuel supplied by the fuel supply device 3 is reduced.