To electrically and reliably connect the operation button of an operation unit to a cord without using a contact point, while preventing the cord from being twisted when handled by a patient.

The operation unit 3 housing the operation button 2 is arranged on the operation unit arrangement surface 7 of a case body 1. A cord exposing part 5 for exposing the cord 4 to the outside is arranged on the cord exposing arrangement surface 8 of the case body 1. The operation unit arrangement surface 7 and the exposing part arrangement surface 8 are arranged on the same axis and also a cover 6 to be rotated around the case body 1 with the axis as a rotation axis is attached to enclose the case body 1. Thus, the operation unit arrangement surface 7 and the cord exposing part arrangement surface 8 are arranged on the same rotation axis and also the cover 6 to be rotated independently from the case body around the case body 1 with the rotation axis as a center is attached, thereby rotating only the cover 6 and preventing the operation unit 3 and the cord exposing part 5 from being rotated.