Provided is a gas seal assembly which includes: an inner sleeve in which a rotation axle is inserted; a rotational sealing sleeve inserted into the inner sleeve; a sealing sleeve contacting the rotational sealing sleeve; a forcing sleeve forcing the sealing sleeve towards the rotational sealing sleeve by contacting the sealing sleeve; a seal housing separated by a predetermined distance from the forcing sleeve and the sealing sleeve and supporting the forcing sleeve; and an elastic part mounted between the seal housing and the forcing sleeve and providing a restoring force to the forcing sleeve, wherein the seal housing protrudes in a center direction of the rotation axle and includes a supporting protrusion for supporting one end of the forcing sleeve.