A gas fire-extinguishing apparatus, comprising: an ejection head having a nozzle section which ejects high-pressure fire-extinguishing gas to a space; a conduit pipe which is connected to the ejection head and guides high-pressure fire-extinguishing gas to the ejection head; a fire-extinguishing gas supply source which supplies the high-pressure fire-extinguishing gas to the conduit pipe; and characterised in that a silencer which is disposed between the ejection head and the conduit pipe and attenuates the sound caused by ejection of the fire-extinguishing gas from the nozzle section; wherein the silencer comprises: a cylindrical peripheral wall, a first mounting section detachably connected to the conduit pipe at one end in an axial direction of the peripheral wall, a second mounting section detachably connected to the ejection head at the other end in the axial direction of the peripheral wall, a first end wall formed at one end in the axial direction of the peripheral wall to be perpendicular to an axis of the peripheral wall, and a second end wall formed at the other end in the axial direction of the peripheral wall to be perpendicular to the axis of the peripheral wall, and which defines a space between the second end wall and the ejection head, wherein a penetrating hole is formed so as to penetrate a centre section of the first end wall in a thickness direction thereof, a centre of which is on the axis of the peripheral wall, and a plurality of penetrating holes are formed so as to penetrate the second end wall in a thickness direction thereof not in the centre section of the end wall. an ejection head having a nozzle section which ejects high-pressure fire-extinguishing gas to a space; a conduit pipe which is connected to the ejection head and guides high-pressure fire-extinguishing gas to the ejection head; a fire-extinguishing gas supply source which supplies the high-pressure fire-extinguishing gas to the conduit pipe; and characterised in that a silencer which is disposed between the ejection head and the conduit pipe and attenuates the sound caused by ejection of the fire-extinguishing gas from the nozzle section; wherein the silencer comprises: a cylindrical peripheral wall, a first mounting section detachably connected to the conduit pipe at one end in an axial direction of the peripheral wall, a second mounting section detachably connected to the ejection head at the other end in the axial direction of the peripheral wall, a first end wall formed at one end in the axial direction of the peripheral wall to be perpendicular to an axis of the peripheral wall, and a second end wall formed at the other end in the axial direction of the peripheral wall to be perpendicular to the axis of the peripheral wall, and which defines a space between the second end wall and the ejection head, wherein a penetrating hole is formed so as to penetrate a centre section of the first end wall in a thickness direction thereof, a centre of which is on the axis of the peripheral wall, and a plurality of penetrating holes are formed so as to penetrate the second end wall in a thickness direction thereof not in the centre section of the end wall. a cylindrical peripheral wall, a first mounting section detachably connected to the conduit pipe at one end in an axial direction of the peripheral wall, a second mounting section detachably connected to the ejection head at the other end in the axial direction of the peripheral wall, a first end wall formed at one end in the axial direction of the peripheral wall to be perpendicular to an axis of the peripheral wall, and a second end wall formed at the other end in the axial direction of the peripheral wall to be perpendicular to the axis of the peripheral wall, and which defines a space between the second end wall and the ejection head, wherein a penetrating hole is formed so as to penetrate a centre section of the first end wall in a thickness direction thereof, a centre of which is on the axis of the peripheral wall, and a plurality of penetrating holes are formed so as to penetrate the second end wall in a thickness direction thereof not in the centre section of the end wall.