An architectural 3D printing apparatus that utilizes a replaceable material capsule comprises: a material extrusion unit is configured to move a piston in a forward direction, pressurize a printing material stored in a material capsule, and extrude the printing material; and a capsule fixing unit is positioned beneath the material extrusion unit and is coupled to the material capsule, ensuring that the inner storage space of the material capsule, which contains the printing material, is aligned with the piston, wherein the material capsule comprises: a body designed in a columnar shape with an open top surface, which contains the inner storage space formed therein; and a nozzle is attached to the bottom surface of the body, through which the printing material is discharged.