A circulation type aquaculture method and a circulation type aquaculture apparatus which treat and remove ammonia harmful to fishes/shellfishes. The method includes a first step of finding an ammonia decomposition rate upon preliminarily treating 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 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 to the aquaculture tank.