An object of the present invention is to provide a circulation type aquaculture method and a circulation type aquaculture apparatus which treat and remove ammonia harmful to fishes/shellfishes, while preventing generation of toxic oxidants caused by an excessive treatment, so as to carry out an ammonia removing treatment in accordance with an increase/decrease of the amount of ammonia discharged from fishes/shellfishes, thereby making it possible to prevent the accumulation of ammonia in cultivation water. In order to achieve this object, the method is proposed in which cultivation water in a circulation type aquaculture tank for rearing aquatic organisms is treated by an aquaculture apparatus main body, and this method is provided with means having a first step of finding an ammonia decomposition rate upon preliminarily treating the cultivation water by using ozone or hypochloric acid so as to set a target remaining amount of ammonia after the decomposing treatment, a second step of finding the amount of ammonia in cultivation water so as to calculate a treating period of time required for reducing the amount of ammonia to the target remaining amount of ammonia based upon the ammonia decomposition rate of the first step, a third step of treating the cultivation water by using ozone or hypochloric acid during the treating period of time calculated in the second step so as to treat and decompose ammonia in the cultivation water and a fourth step of returning the cultivation water that has been subjected to the decomposing treatment in the third step to the aquaculture tank.
