The combustion device (1) of a gas turbine includes burners (2) connected to a front plate (5) of a combustion chamber (3). The front plate (5) has, spaced apart from one another, a front sheet (8) and an impingement sheet (7) with aligned holes (11, 12) housing the burners (2). A piston ring (15) is provided between the front sheet (8) and impingement sheet (7) to seal the holes (11, 12). The axial length of the border of the hole (11, 12) of the front sheet (8) and/or impingement sheet (7) is longer than the thickness of the corresponding front sheet (8) and/or impingement sheet (7).