Recently, bactericidal radiation (253.7nm) has been widely used to not only sterilizing but also semiconductor, food industries and so on. However, the ways of calibration for the radiation sources and/or the radiometers have not been established for the bactericidal irradiance. The bactericidal irradiance could be measured by the two ways of spectroradiometry and combining the thermal detector with optical filters. In our measurement, the difference between the values obtained by the two ways was few percents and so it was confirmed that both ways were useful. On use of the thermal detector, the calibration were carried out by following standards and methods: (1) using a total (whole wavelength) irradiance standard, (2) using a luminous intensity standard with broad band-pass filter and (3) using a spectral irradiance standard with broad band-pass filter. The calibrated values of these standards were probably same within 2.5%, it was confirmed that each standard was useful for calibrating the thermal detector. Irradiance of GL-15, which is a typical bactericidal lamp, was measured in the wavelength region of 250-2500nm. As the results, the rate of the bactericidal (253.7nm), another ultra-violet and visible and infrared radiation to total one were about 80%, 8 % and 12% respectively. Most of the infrared radiation was emitted nearby electrodes.