A holding apparatus for holding a semiconductor wafer comprises a pneumatic cylinder, a plunger movably connected to the pneumatic cylinder, an inlet pipe connected to the pneumatic cylinder, and a relief valve connected to the inlet pipe. Clean dry air is pumped into the pneumatic cylinder through the inlet pipe to impel the plunger in a first direction to contact the wafer. A part of the air in the inlet pipe is discharged through the relief valve to regulate air pressure to the pneumatic cylinder.