A foldable 3D printer includes: a main body having an upper surface parallel to the ground; a stage coupled to the upper surface of the main body and adapted to stack a molding material thereon; a nozzle unit spraying the molding material onto the stage; and a bridge assembly adapted to mount the nozzle unit thereon, the bridge assembly being rotatably coupled to the main body to be positioned parallel to the main body when not in use and to be positioned perpendicular to the main body when in use.