PURPOSE: To obtain a sheet excellent in heat and moisture resistance produced by a paper making method using a specified component containing a thermoplastic powder of a specified particle size by coating one of the surfaces of the obtd. sheet with an impregnated layer comprising one or more kinds of plasticizer of the thermoplastic powder described above.

CONSTITUTION: Components of cellulose fibers, non-cellulose fibers, at least one kind of thermoplastic resin powder having 25 to 60 μm average particle size (e.g. a copolymer of vinyl chloride and vinyl acetate), at least one kind of flocculant (e.g. aluminum sulfate), binder (e.g. corn starch), proper fillers and additives are used in the paper making process to produce a sheet. Then water is removed from the sheet, and one of the surfaces of the dried sheet is coated with an impregnated layer containing 10 to 100 parts plasticizer, 0.1 to 4 parts temp. stabilizer, 0 to 10 parts emulsifier, one other binder and inorg. fillers blended into 100 parts of the thermoplastic powder so as to obtain the objective sheet.