Improvement of microbial ammonia oxidation method using a rockwool as a carrier in wastewater treatment was examined through batch and continuous operation. In batch operation, a nitrifying bacterium, Nitrosomonas europaea (NBRC 14298), and phosphorus and iron-complexes were highly attached to the rockwool. In continuous operation, the operation with rockwool (RW) was shortened the hydraulic retention time (HRT) from 20h to 10h, and the maximum ammonia removal ratio was 87.5%. The average of ammonia removal ratio was performed 73.1%, 78.2% at 20h and 10h, respectively, at aeration rate of 3000ml·min^-1. The ammonia oxidation rate was 22.3mg-N·l^-1-carrier·h^-1 when the ammonia loading rate was 25.5mg-N·l^-1-carrier·h^-1. Quantitative PCR results revealed that around 10¹⁵ cells·l^-1-carrier were immobilized to the RW. Therefore, the RW could retain a large number of nitrifying bacteria, improve the degree of nitrification and have widely application.