To press ferrite half bodies against each other with the surfaces of the half bodies which are faced opposite to each other.

A noise-suppressing device is integrally formed with case half bodies 19, a coupling means which holds the half bodies 19 in a closed position such that the bodies 19 are jointed together around a cable with their upper openings being brought into contact with each other in a state where they are faced opposite to each other, and a half body 14, which is housed in the half body 19, having a core passage 16 and a surface 15, whose surface 15 is abutted with so as to make the cable insert to a groove when the body 19 is in the closed position, and the core passage 16 of which is overlaped, and is made to protrude into space and abut to the ferrite half body 14. A platform 40 is protruded to the bottom 24 of the other half body 19 separately from the sidewalls 20 and 22 and end walls 26 and 28 of the half body 19 for swinging the half body 14, when the half body 14 comes into contact within the platform 40. By jointing the half bodies 19 together, the surface 15 of the half body 14 comes into contact with the platform 40 around a cable which is passed through the passage 16.