PURPOSE: To clean an intake air filter in a simple and inexpensive manner by cooling bleed air from a gas turbine compressor by means of a cooling device provided to an air intake device of the gas turbine so as to use it as pulse air.

CONSTITUTION: A cooling device 20 which is composed of a curved pipe for heat exchanging, is provided in a flow path of a clean air 4 in an air intake device 1, and the cooling device 20 is arranged between a bleed air pipe 18 from a gas turbine compressor 6 and a pulse air pipe 5. The time when the internal pressure in the air intake device 1 is lowered, is detected by a difference pressure detecting switch 9, and a solenoid value 12 is operated by control means 14 and 11 so as to inject pulse air 16 into an intake filter 3 for blowing deposits off. In this case, bleed air from the gas turbine compressor 6 is cooled by allowing the cooling device 20 to effect heat-exchanging with clean air 4 so as to inject the cooled bleed air against the intake filter 3.