PURPOSE: To provide a method for treating various kinds of high concentration ammonia waste waters which is desirable viewed in the light of environment and heat balance and whose treatment efficiency is high and which is easily put to practical use when a high concentration ammonia waste liquid is treated.

CONSTITUTION: A zeolite regeneration 38 or a sewage sludge dehydration filtrate 43 which is a high concentration ammonia waste liquid is mixed with sewage sludge 42 by an appropriate amount, and catalytic wet oxidation treatment is applied to the minute to remove ammonia. This method is made fundamental. Besides, a method where both electrodialysis treatment and ammonia stripping treatment are jointly used and a method where after a soluble magnesium salt or a soluble cobalt salt is added to adjust the liquid to pH 8-10, a soluble phosphate is added by an appropriate amount and mixed, causing crystallization where ammonia in the solution is crystallized as insoluble crystal to be performed, allowing the crystal to be removed by sedimentation and separation are provided.