A top port apparatus for air suspension, comprising: a middle casing; a top casing coupled to an upper side of the middle casing and configured to be connected to a vehicle body; a bottom casing coupled to a lower side of the middle casing and configured to be connected to an air spring; and a sealing section configured to seal a gap among the middle casing, the top casing, and the bottom casing, wherein the middle casing comprises: a middle casing body disposed between the top casing and the bottom casing and having a valve chamber; and a seating part protruding outward from the middle casing body and extending along a circumferential surface of the middle casing body, wherein the top casing comprises: a top casing body having a first chamber connecting with the valve chamber; and a first extension part protruding outward from the top casing body and seated on an upper side of the seating part, and wherein the bottom casing comprises: a bottom casing body having a second chamber and a third chamber connecting with the valve chamber; and a second extension part protruding outward from the bottom casing body and seated on a lower side of the seating part. a middle casing; a top casing coupled to an upper side of the middle casing and configured to be connected to a vehicle body; a bottom casing coupled to a lower side of the middle casing and configured to be connected to an air spring; and a sealing section configured to seal a gap among the middle casing, the top casing, and the bottom casing, wherein the middle casing comprises: a middle casing body disposed between the top casing and the bottom casing and having a valve chamber; and a seating part protruding outward from the middle casing body and extending along a circumferential surface of the middle casing body, wherein the top casing comprises: a top casing body having a first chamber connecting with the valve chamber; and a first extension part protruding outward from the top casing body and seated on an upper side of the seating part, and wherein the bottom casing comprises: a bottom casing body having a second chamber and a third chamber connecting with the valve chamber; and a second extension part protruding outward from the bottom casing body and seated on a lower side of the seating part. a middle casing body disposed between the top casing and the bottom casing and having a valve chamber; and a seating part protruding outward from the middle casing body and extending along a circumferential surface of the middle casing body, wherein the top casing comprises: a top casing body having a first chamber connecting with the valve chamber; and a first extension part protruding outward from the top casing body and seated on an upper side of the seating part, and wherein the bottom casing comprises: a bottom casing body having a second chamber and a third chamber connecting with the valve chamber; and a second extension part protruding outward from the bottom casing body and seated on a lower side of the seating part. a top casing body having a first chamber connecting with the valve chamber; and a first extension part protruding outward from the top casing body and seated on an upper side of the seating part, and wherein the bottom casing comprises: a bottom casing body having a second chamber and a third chamber connecting with the valve chamber; and a second extension part protruding outward from the bottom casing body and seated on a lower side of the seating part. a bottom casing body having a second chamber and a third chamber connecting with the valve chamber; and a second extension part protruding outward from the bottom casing body and seated on a lower side of the seating part.