To provide a electromagnetic noise suppressor capable of efficiently suppressing the radiation noise as well as grounding a shield cable by a simple work.

Within this electromagnetic noise suppressor, a shield cable 40 is held between the first case half body 2a and the second case half body 2b so as to close the space between the two half bodies 2a and 2b as well as the casing 44 of the shield cable 40 is broken through by a sharp key type part 15 of a clamp piece 4A so as to be brought into electric contact with a shield layer 43 so that the high-frequency current running in the shield layer 43 may be grounded through the intermediary of the clamp piece 4A for suppressing the radiation noise from the shield cable 40.