A mask-mounting apparatus for an exposure machine, comprising: a mask frame configured to secure a mask; a gas cell (6; 7) provided beneath the mask frame and configured to support the mask frame; a gas-supply pipeline; and a gas-supply unit arranged to supply gas to the gas cell (6; 7) and to communicate with the gas cell (6; 7) via the gas-supply pipeline; wherein the gas-supply pipeline is provided thereon with a pneumatic switch valve (10; 11), the pneumatic switch valve being arranged so that, in use, in the event of interruption of supply from the gas-supply unit, the pneumatic switch valve (10; 11) shuts off the gas-supply pipeline, to prevent the gas cell (6; 7) from being deflated, characterized in that: the gas-supply pipeline comprises a plurality of branch gas-supply pipelines arranged to communicate with the gas cell (6; 7), and a control pipeline arranged to communicate with the gas-supply unit and the plurality of branch gas-supply pipelines; the control pipeline is further provided thereon with a vent valve, a master pressure-reducing valve, a master pressure gauge, and a master pneumatic switch valve; and the vent valve, the master pressure-reducing valve and the master pressure gauge are provided at the end of the control pipeline proximate to the gas-supply unit, the master pneumatic switch valve is provided at the other end of the control pipeline proximate to the gas cell (6; 7). a mask frame configured to secure a mask; a gas cell (6; 7) provided beneath the mask frame and configured to support the mask frame; a gas-supply pipeline; and a gas-supply unit arranged to supply gas to the gas cell (6; 7) and to communicate with the gas cell (6; 7) via the gas-supply pipeline; wherein the gas-supply pipeline is provided thereon with a pneumatic switch valve (10; 11), the pneumatic switch valve being arranged so that, in use, in the event of interruption of supply from the gas-supply unit, the pneumatic switch valve (10; 11) shuts off the gas-supply pipeline, to prevent the gas cell (6; 7) from being deflated, characterized in that: the gas-supply pipeline comprises a plurality of branch gas-supply pipelines arranged to communicate with the gas cell (6; 7), and a control pipeline arranged to communicate with the gas-supply unit and the plurality of branch gas-supply pipelines; the control pipeline is further provided thereon with a vent valve, a master pressure-reducing valve, a master pressure gauge, and a master pneumatic switch valve; and the vent valve, the master pressure-reducing valve and the master pressure gauge are provided at the end of the control pipeline proximate to the gas-supply unit, the master pneumatic switch valve is provided at the other end of the control pipeline proximate to the gas cell (6; 7). the gas-supply pipeline comprises a plurality of branch gas-supply pipelines arranged to communicate with the gas cell (6; 7), and a control pipeline arranged to communicate with the gas-supply unit and the plurality of branch gas-supply pipelines; the control pipeline is further provided thereon with a vent valve, a master pressure-reducing valve, a master pressure gauge, and a master pneumatic switch valve; and the vent valve, the master pressure-reducing valve and the master pressure gauge are provided at the end of the control pipeline proximate to the gas-supply unit, the master pneumatic switch valve is provided at the other end of the control pipeline proximate to the gas cell (6; 7).