An optical connector-incorporating plug comprising: an optical cable with an optical fiber being taken out from a cable end portion of the optical cable a cable insertion component having an insertion hole in which the optical cable is inserted with the optical fiber being taken out from the cable end portion of the optical cable; a tubular member in which the cable end portion and the optical fiber are placed and in which the cable insertion component is fitted; a hole formed at a peripheral wall of the tubular member at a position where at least one of the cable end portion and the optical fiber in the tubular member is seeable through the hole; and a surrounding member mounted to the tubular member to surround at least a part of the peripheral wall of the tubular member and thereby cover the hole, characterized in that the optical connector-incorporating plug further comprises: a plurality of seal members (201,202) disposed in a gap between an outer peripheral surface of the tubular member and an inner peripheral surface of the surrounding member to seal the gap over a whole circumference of the outer peripheral surface of the tubular member, wherein the plurality of seal members are situated away from each other in a direction of a central axis of the tubular member, and the hole is situated between the plurality of seal members in the direction of the central axis of the tubular member. an optical cable with an optical fiber being taken out from a cable end portion of the optical cable a cable insertion component having an insertion hole in which the optical cable is inserted with the optical fiber being taken out from the cable end portion of the optical cable; a tubular member in which the cable end portion and the optical fiber are placed and in which the cable insertion component is fitted; a hole formed at a peripheral wall of the tubular member at a position where at least one of the cable end portion and the optical fiber in the tubular member is seeable through the hole; and a surrounding member mounted to the tubular member to surround at least a part of the peripheral wall of the tubular member and thereby cover the hole, characterized in that the optical connector-incorporating plug further comprises: a plurality of seal members (201,202) disposed in a gap between an outer peripheral surface of the tubular member and an inner peripheral surface of the surrounding member to seal the gap over a whole circumference of the outer peripheral surface of the tubular member, wherein the plurality of seal members are situated away from each other in a direction of a central axis of the tubular member, and the hole is situated between the plurality of seal members in the direction of the central axis of the tubular member. a plurality of seal members (201,202) disposed in a gap between an outer peripheral surface of the tubular member and an inner peripheral surface of the surrounding member to seal the gap over a whole circumference of the outer peripheral surface of the tubular member, wherein the plurality of seal members are situated away from each other in a direction of a central axis of the tubular member, and the hole is situated between the plurality of seal members in the direction of the central axis of the tubular member.