Abstract: A gas turbine suction air filter is provided wherein, despite a large capacity, dust is easily removed by an ultrasonic washer. A gas turbine suction air filter (1) has a box-like frame member (3) and a filter cloth (5) contained in the frame member (3). The frame member (3) is made of a metal material, preferably a stainless steel. The filter cloth (5) is formed having many pleats so that many folded faces (7) are formed. No intervening member is provided between adjacent folded faces (7, 7), with only a space being arranged there. The filter cloth (5) is a non-woven fabric of a synthetic resin fiber, preferably a polypropylene fiber. While this filter (1) has a large capacity, an ultrasonic wave reaches the entire filter cloth (5) when the filter (1) is washed by an ultrasonic washer.