According to an embodiment, a multi-layer antenna structure comprises a printed circuit board including an IC for processing an RF signal, a feeding line connected to the IC, and a feeding pad connected to the feeding line, a conductive lower layer tightly contacting the printed circuit board and including a feeding hole in an area connected with the feeding pad and vertically open and a waveguide connected to the feeding hole and disposed on an upper surface thereof, and a conductive upper layer tightly contacting the conductive lower layer and including an antenna slot pattern in an area corresponding to the waveguide and vertically open. The waveguide may include a bottom surface positioned lower than an upper surface thereof, a side surface extending from each of two opposite ends of the bottom surface to the upper surface, and a protrusion protruding upward from a center portion of the bottom surface.