A reflection characteristic in a high frequency region at a feeding point into a strip line is improved and the assembly of a strip line feeding apparatus facilitated by the method and apparatus herein. The strip line includes a strip line pattern on a surface of a first dielectric substrate having a ground conductor pattern disposed on the opposite surface thereof, and a second ground conductor pattern disposed on a surface of a second dielectric substrate. A serial high impedance portion is disposed at an area near the tip portion of the strip line pattern. The high impedance portion includes a portion of the strip line pattern having narrowed width or a hole disposed under a through-hole for an inner conductor, which electrically connects the strip line pattern and an inner conductor. Dimensions of the high impedance portion are controlled to cancel out parasitic susceptance due to the discontinuous structure. A matching through-hole is further disposed in the second dielectric substrate in an area separated from the tip portion of the strip line pattern by a distance of around 25% of the typical wave length. The matching through-hole is elongated to a land pattern in a hole disposed in the second ground conductor pattern so as to electrically connect the conductor strip pattern and the land pattern.