1. A printed object surface-treatment type 3D printer for construction, comprising: a movable body (20); a nozzle (10) mounted on the movable body (20); a spray pipe (60) configured to follow the nozzle (10); and a plurality of spray holes (61) mounted on the spray pipe (60), wherein the nozzle (10) is configured to discharge a fluid material, wherein the spray pipe (60) is configured to move along with movement of the movable body (20) and the nozzle (10), wherein the spray pipe (60) is connected to the movable body (20) via a support shaft (40), an elevating body (41) and a rotatable body 30, wherein a range between the spray pipe (60) and a printed object is adjusted as the spray pipe (60) is lifted or lowered along with the support shaft (40) being lifted or lowered by the elevating body (41) connected to an upper end of the support shaft (40), wherein the plurality of spray holes (61) are mounted on the spray pipe (60) in a direction perpendicular to the discharge direction of the fluid material from the nozzle (10), and is configured to spray the fluid material onto a side surface of a wall body of the printed object extruded from the nozzle (10).