A high permittivity LSE-NRD guide was applied to a planar antenna at 60 GHz. Emphasis was placed on compatibility between the high permittivity LSE-NRD guide and the conventionally used low permittivity LSM-NRD guide. Performance of the transition between two such types of NRD guides was optimized by using an electromagnetic simulator and the validity was experimentally demonstrated. A simple radiator, consisting of a tapered high permittivity LSE-NRD guide was fabricated and evaluated as to radiation characteristics. Since the radiator has a broad radiation pattern, it was employed in a primary radiator of a two-dimensional parabolic reflector to develop a new type of folded planar antenna at 60 GHz. This planar antenna has a double-layered structure. In the upper layer, a metalized dielectric substrate with a slotted array is excited by a rectangular-shaped oversized waveguide, and in the lower layer, an offset parabolic reflector is fed by the radiator. Measurement showed the half-power beam width of the fabricated antenna to be 2.5 degrees in the E and H planes, respectively, and the gain to be 35.3 dBi, thus indicating that a good pencil beam antenna was successfully developed in this manner.