The invention relates to an envelope of plastic sheet material consisting of a thermoplastic sheet, which is laminated to a sheet of hydrophilic material at least on the side forming the outside of the envelope. The flap belonging to the envelope is laminated to a paper layer at least on its inside, said layer supporting a gumming. The invention also relates to a method for continuously making such envelopes, a web of a plastic sheet laminated according to the above being folded with its edge portions towards a central area, which is left free. One or more paper webs are laminated to this central area and punched-out areas are made in the central area to a desired shape of the flaps of the envelopes. The envelopes are thereafter sealed along their sides by means of transversal welding seams and separated from each other.
