To obtain the subject impregnated paper high in dimensional stability, durable even under severe waterproof conditions, and alternative to metallic aluminum used in drink and food cans, by impregnating a sheet of paper with a specific impregnant bearing a combination of both organic and inorganic material characteristics.

This impregnated paper is obtained by impregnating a sheet of paper with an impregnant (described below) which is prepared by reaction of a dicarboxylic acid anhydride of formula II (R4 is a 1-8C alkyl or the like) with the hydroxyl group of a cellulose carboxylic acid diester of formula I (R1 is OH or any of various ester groups described below; R2 and R3 are each a 2-4C lower alkyl ester group, nitric ester group or the like; the overall ester group substitution degree is 2.0-2.7; (n)≥10) to introduce reactive carboxyl group into the above diester followed by reaction of a silane coupling agent of formula III (R5 to R7 are each a 1-4C alkyl; R8 is glycidyl or the like), and then carrying out hydrolysis-condensation of the alkoxysilyl group site to obtain the above aimed impregnant of formula IV ((m) is ≥1; R9 is a compound portion having such a structure that the epoxy groups are subjected to ring opening polymerization).