To provide an acoustic device capable of enlarging a frequency zone having high sound absorbing rate and to provide a combustor and a gas turbine.

An acoustic liner 20 is annularly mounted on the combustor 10 of the gas turbine 1 and is composed of a housing 21 and a porous plate 25. A resonance space 23 is formed by the housing 21 and the porous plate 25. A recessed part 30 and a through hole 26 are formed in the porous plate 25, the recessed part 30 is opened on an acoustic face 27 of the porous plate 25, and the through hole 26 communicates a sound source face 28 of the porous plate 25 with the recessed part 30. Consequently, since the recessed part 30 is formed in the porous plate 25 when absorbing sound due to combustion vibration caused when burning fuel in the combustor 10 by the acoustic liner 20, total length of the through hole 26 can be reduced, and a scope of resonance frequency for absorbing sound is enlarged. As a result, the frequency zone having high sound absorbing rate can be widened.