PURPOSE: To provide a shield room, which can transmit only a specified radiowave from the outside into the inside suppressing penetrating noises at this time, at a low cost.

CONSTITUTION: A receiving antenna 21 and an external relay device 12 are provided at the outside of an electromagnetic shielding body 11. The external relay device 12 receives extrinsic radiowaves by using the receiving antenna 21, converts the radiowaves into the electric signals, selects only the signal having a specified frequency, converts the signal into the optical signal and outputs the optical signal. An optical fiber 13 penetrates the side surface of the electromagnetic shielding body 11 and optically connects the external relay device 12 and an internal relay device 14. The optical signal outputted from the external relay device 12 is transmitted from the outside of the electromagnetic shielding body 11 into the inside through the optical fiber 13 and inputted into the internal relay device 14. The internal relay device 14 converts the inputted optical signal into the electric signal and transmits the signal as the radiowave by using a transmitting antenna 33.