PURPOSE: To obtain an attenuator attachable to and detachable from the primary radiator of a parabolic antenna by forming a caplike attenuator using synthetic resin material such as ABC resin etc.

CONSTITUTION: The attenuator 4 is formed of synthetic resin material such as ABC resin, fluororesin etc. and the shape is bottomed cylindrical (caplike). The attenuator 4 is attachable to the opening 3 at the tip of a primary radiator provided at the focal point of a parabolic antenna reflection mirror. The amount of attenuation of the attenuator 4 is determined by dielectric loss of synthetic resin material that forms the attenuator 4 and thickness (t) of a wave attenuation wall 19. The attenuator thus formed can be utilized for checking performance of a satellite broadcast receiving device. Thus, an attenuator attachable to and detachable from the primary radiator of a parabolic antenna can be obtained.