A printer, comprising: a housing provided with an opening; a print medium container built in the opening of the housing, the print medium container being capable of containing a print medium, the print medium including an adhesive agent layer on one surface thereof; an opening and closing cover attached to the housing and configured to open and close the print medium container; a feed roller rotatably supported by the opening and closing cover and configured to feed the print medium; and a print head mounted opposing the feed roller, the print head being configured to perform printing on the print medium, wherein the opening and closing cover is provided with a head on a free end thereof, the head gradually reducing in thickness toward a tip thereof, wherein the head includes: a first surface configured to face the print medium container when the opening and closing cover is set in a closed state; a second surface configured to face the adhesive agent layer of the print medium when the print medium is fed from the print medium container toward the feed roller, the second surface provided with a ridge part projecting therefrom; and an end surface disposed at a tip of the opening and closing cover and configured to face a feeding path of the print medium, the feeding path located between the print medium container and the feed roller, the end surface provided with a ridge part for projecting therefrom toward the adhesive agent layer of the print medium, characterized in that the ridge part projecting from the end surface has a longer projecting length toward the adhesive agent layer of the print medium than the ridge part projecting from the second surface. a housing provided with an opening; a print medium container built in the opening of the housing, the print medium container being capable of containing a print medium, the print medium including an adhesive agent layer on one surface thereof; an opening and closing cover attached to the housing and configured to open and close the print medium container; a feed roller rotatably supported by the opening and closing cover and configured to feed the print medium; and a print head mounted opposing the feed roller, the print head being configured to perform printing on the print medium, wherein the opening and closing cover is provided with a head on a free end thereof, the head gradually reducing in thickness toward a tip thereof, wherein the head includes: a first surface configured to face the print medium container when the opening and closing cover is set in a closed state; a second surface configured to face the adhesive agent layer of the print medium when the print medium is fed from the print medium container toward the feed roller, the second surface provided with a ridge part projecting therefrom; and an end surface disposed at a tip of the opening and closing cover and configured to face a feeding path of the print medium, the feeding path located between the print medium container and the feed roller, the end surface provided with a ridge part for projecting therefrom toward the adhesive agent layer of the print medium, characterized in that the ridge part projecting from the end surface has a longer projecting length toward the adhesive agent layer of the print medium than the ridge part projecting from the second surface. a first surface configured to face the print medium container when the opening and closing cover is set in a closed state; a second surface configured to face the adhesive agent layer of the print medium when the print medium is fed from the print medium container toward the feed roller, the second surface provided with a ridge part projecting therefrom; and an end surface disposed at a tip of the opening and closing cover and configured to face a feeding path of the print medium, the feeding path located between the print medium container and the feed roller, the end surface provided with a ridge part for projecting therefrom toward the adhesive agent layer of the print medium, characterized in that the ridge part projecting from the end surface has a longer projecting length toward the adhesive agent layer of the print medium than the ridge part projecting from the second surface.