The electron cyclotron emission ~ECE! diagnostic system is installed on the large helical device ~LHD!. The system includes the following instruments: a heterodyne radiometer, a Michelson spectrometer, and a grating polychromator. A 63.5 mm corrugated waveguide system is fully utilized. Large collection optics and notch filters at the frequency of the electron cyclotron heating ~ECH! were developed for this system. In addition to these filters, the rectangular waveguidenotch filters, the ECE measurement with the radiometer has been successfully performed during the ECH.