PURPOSE: To prevent damages from occurring to screens and substrates to be processed by a method wherein operations of the entire printing apparatus are controlled, based on outputs from a position detecting means that detects positions in the vertical direction for substrate pressing parts.

CONSTITUTION: A single or a plurality of substrate pressing parts 13 and 15 are provided to a fist clamping device 31 so that they can move in the first direction for bringing one end thereof into contact with one side of a substrate 2 and in the second direction that is contrary to the first direction. Elastic members 16 bring each one end of the substrate pressing parts 13 and 15 into pressure contact with one side of the substrate 2 with the corresponding substrate pressing part 13 or 15 energized when the substrate 2 is corrected to become flat. Furthermore, a position detecting means 32 detects positions of the substrate pressing parts 13 and 15 in the first and the second directions. The state of warping of the substrate 2 or the state of unevenness on the surface of the substrate 2 can be judged, based on outputs from the position detecting means 32. Operations of the entire apparatus 30 is controlled, based on outputs from the position detecting means 32, and damages can be prevented from occurring to the substrate 2 and a screen 22 to be used in the printing process.