The denitrifiers isolated from the activated sludge of night soil treatment plant were immobilized using a photo-crosslinkable resin prepolymer. Denitrifying activity was strongly inhibited during the first period but the activity was increased in the medium containing nitrate and recovered after 1 day. Acetate was an effective hydrogen source and soap was also effective. Methanol could not serve as a hydrogen source. The optimum pH for denitrification by the immobilized bacteria was 7.0 for nitrite and 7.5 for nitrate, and the optimum temperature ranged 30℃ to 40℃. The lowest CH3COONa/NOx-N ratio nessary for getting the highest activity was 4 for nitrite (BOD/NO2-N＝2) and 5 for nitrate (BOD/NO3-N＝2.5). Photo-crosslinkable resin prepolymer gels exhibited stable denitrification activity to the secondarily treated sewage contained 70mg/l of soap.