To utilize a recycling of a copied or printed sheet by using many times the copied or printed sheet.

Coloring matter dyes of three primary colors which develop colors in alkaline properties and an iodo-starch dye which develops black color are respectively regulated in a chromaticity and a viscosity with solvents. Then, they are set in an ink jet unit. A sheet is color printed by using a printer having the jet unit. When the printed sheet becomes unnecessary, the sheet is sprayed with organic or inorganic acid dilute solution or reducer solution, or coated with it by a roller. Or, it is fumigated by these drugs to simultaneously erase the four colors. After it is dried, the sheet is recycled.