To accurately position a horizontal angle by very easily fine-adjusting a position of a radiation feeding part including a primary radiator in a short time.

The antenna system is configured with a main reflecting mirror that is supported by a support, a radiation feeding section 14 that has a primary radiator 13 receiving a radio wave reflected from the main reflecting mirror, and the support 15 that places the radiation feeding section 14 at a focal position of the main reflection mirror. A support section 21 whose support wall 23 is formed at both sides of a radiation feeding section mount face 22 with a fitting groove 24 formed therein is formed at a tip of the support 15. The radiation feeding section 14 is disposed on the radiation feeding section mount face 22 by fitting a fitting projection 25 to the fitting groove 24. The radiation feeding section 14 is moved in a horizontal direction and nearly in parallel with the main reflection mirror by using a fine-adjustment screw 27 screwed to a thread hole 26 formed in the support wall 23 to fine-adjust the horizontal angle.