The door for the companion animal according to the present invention may be a partially opened sliding door or an auxiliary door which can be fitted between the door and the door An auxiliary door cutter formed below the auxiliary door frame to penetrate the auxiliary door frame A pair of rotation axis end insertion portions communicating with the auxiliary door cutout portion and being opposed to each other on one side of the upper side of the side frame of the auxiliary auxiliary door frame located on both sides of the auxiliary door cutout portion A rotating shaft member into which both end portions are inserted into the pair of rotating shaft end inserting portions An auxiliary door formed of transparent or semitransparent material which is rotatably coupled to the inner side of the auxiliary door cutout part by having a rotary shaft body insertable part that can be inserted in a direction perpendicular to the longitudinal direction of the rotary shaft member A rotary shaft member fixing unit fixed to the rotary shaft body by inserting the rotary shaft member into the rotary shaft body insertion unit and closing the rotary shaft body insertion unit so as not to protrude from the auxiliary door An auxiliary door rotating shaft height information portion formed to cover an area including the rotating shaft body insertion portion in the auxiliary door and attached to the auxiliary door and being larger than the rotation shaft body insertion portion And a rotary shaft end high rigidity portion covering the pair of rotary shaft end insertion portions such that both side ends of the rotary shaft member inserted into the pair of rotary shaft end inserting portions are not separated from the rotary shaft end inserting portion.본 발명에 따른 반려동물 전용 출입문은 부분적으로 열린 미닫이문 또는 미서기문과 문틀 사이에 끼워질 수 있는 보조문틀 상기 보조문틀 하부에 상기 보조문틀을 관통하도록 형성된 보조문 절개부 상기 보조문 절개부의 양 측면에 위치된 측면 보조문틀 테두리의 상부 일측에 상기 보조문 절개부와 연통되고 서로 대향되도록 형성된 한 쌍의 회전축 단부 삽입부 상기 한 쌍의 회전축 단부 삽입부에 양측 단부가 삽입되는 회전축 부재 상기 회전축 부재가 상기 회전
