A method of preparing a plastic mask for paste printing with a plastic sheet being provided with an area containing a predetermined pattern including one or more through-holes is carried out by the steps of bringing the plastic mask provided with electroconductive material on at least one surface into close contact with a printing material while applying an electrical ground potential to the electroconductive material and then using the mask for paste printing by spreading and pressing a past to cause it to pass through any of the through-holes forming the predetermined pattern for deposit on the printing material and then removing the mask from the printing material to leave the paste printing pattern.