A printer, comprising: a housing; a print medium container built in the housing, the print medium container configured to accommodate a print medium, the print medium including an adhesive agent layer on one surface thereof; an opening and closing cover disposed on the housing and configured to open and close; a feed roller rotatably disposed on a free end of the opening and closing cover, the feed roller being configured to feed the print medium; a print head disposed to face the feed roller in the housing, the print head being configured to perform printing on the print medium; a first 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 in a closed state of the opening and closing cover; a second ridge part disposed on the first surface, the second ridge part protruding from the first surface; and a third ridge part disposed on the first surface, the third ridge part protruding from the first surface, the third ridge part being located on an extension of the second ridge part in a direction in which the second ridge part extends; characterized in that the printer further comprises a protruding part disposed on a feed roller side end of the first surface and protruding in an intersecting direction with the first surface to face the feed roller; and a first ridge part protruding from a surface of the protruding part; wherein the third ridge part is spaced apart from the second ridge part; the second ridge part extends in an intersecting direction with a lengthwise direction of the feed roller to continuously connect to the first ridge part; the opening and closing cover includes a protruding head having a thickness that is gradually narrower in a direction away from the feed roller, the protruding head being disposed on the free end of the opening and closing cover, the protruding head includes the first surface, a second surface and a connecting part connecting the first surface and the second surface, the first surface being 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 in the closed state of the opening and closing cover, the second surface facing the print medium container in the closed state of the opening and closing cover, the connecting part being disposed on a tip of the protruding head, and the second ridge part ends in a position between the feed roller and the connecting part, and the third ridge part being disposed on the first surface on a side thereof close to the connecting part. a housing; a print medium container built in the housing, the print medium container configured to accommodate a print medium, the print medium including an adhesive agent layer on one surface thereof; an opening and closing cover disposed on the housing and configured to open and close; a feed roller rotatably disposed on a free end of the opening and closing cover, the feed roller being configured to feed the print medium; a print head disposed to face the feed roller in the housing, the print head being configured to perform printing on the print medium; a first 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 in a closed state of the opening and closing cover; a second ridge part disposed on the first surface, the second ridge part protruding from the first surface; and a third ridge part disposed on the first surface, the third ridge part protruding from the first surface, the third ridge part being located on an extension of the second ridge part in a direction in which the second ridge part extends; characterized in that the printer further comprises a protruding part disposed on a feed roller side end of the first surface and protruding in an intersecting direction with the first surface to face the feed roller; and a first ridge part protruding from a surface of the protruding part; wherein the third ridge part is spaced apart from the second ridge part; the second ridge part extends in an intersecting direction with a lengthwise direction of the feed roller to continuously connect to the first ridge part; the opening and closing cover includes a protruding head having a thickness that is gradually narrower in a direction away from the feed roller, the protruding head being disposed on the free end of the opening and closing cover, the protruding head includes the first surface, a second surface and a connecting part connecting the first surface and the second surface, the first surface being 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 in the closed state of the opening and closing cover, the second surface facing the print medium container in the closed state of the opening and closing cover, the connecting part being disposed on a tip of the protruding head, and the second ridge part ends in a position between the feed roller and the connecting part, and the third ridge part being disposed on the first surface on a side thereof close to the connecting part.