An apparatus for forming slant, linear easy-to-tear portions on a long plastic film, comprising a roll on which the long plastic film passes, pluralities of pattern rolls each partially having a slant, linear stamp on a rolling surface, a shaft to which pluralities of the pattern rolls are fixed, and a first mechanism for moving the shaft in a direction to the roll. Pressure rolls pushing the pattern rolls via rolls fixed to the shaft. A second moving mechanism for moving the pressure rolls in a direction to the pattern rolls, whereby with the pressure rolls pushing the pattern rolls by the second moving mechanism, the stamp of the pattern rolls are pressed onto the elastic film by the first moving mechanism, so that the slant, linear easy-to-tear portions with recesses formed by the pattern projections of the stamp are provided partially and periodically on the plastic film.