<p>An attenuation device attenuates a signal received from a first terminal and transmits the attenuated signal from a second terminal. The attenuation device includes: a first transmission path and a second transmission path having different signal attenuation amounts; a connection switching unit arranged between the first terminal and the second terminal for switching connection to the first transmission path or to the second transmission path; and a first grounding switching unit which connects the both ends of the first transmission path and a contact point positioned on the line of the first transmission path to a reference potential when the second transmission path is electrically connected between the first terminal and the second terminal.</p>
