Provided is a dielectric leakage wave antenna in which both transmission characteristics of a dielectric image line for a radiating section and those of a microstrip line for an exciting section are satisfied while enhancing efficiency by such an arrangement as a dielectric substrate has a lower layer portion and an upper layer portion bonded onto the lower layer portion. A ground plate conductor forming the dielectric image line for making an electromagnetic wave propagate through the dielectric substrate direction in a direction intersecting its thickness direction perpendicularly is formed, as one surface side of the dielectric substrate, on the lower surface of the lower layer. A plurality of leakage metal strips provided in parallel at a predetermined interval on the opposite side of the dielectric substrate are formed on the upper surface of the upper layer of the dielectric substrate. A line metal strip forming the microstrip line with the ground plate conductor constituting the exciting section, and a branching means for branching an electromagnetic wave propagating on the microstrip line to a direction intersecting the plurality of leakage metal strips in the dielectric substrate are formed between the upper and lower layers of the dielectric substrate.