NOVELTY - Cultivating anaerobic ammonium-oxidizing bacteria capable of denitrifying ammonium and nitrate substrates, comprising cultivating the bacteria in a cultivation tank, feeding a substrate into the cultivation tank, and controlling a feed rate (Y) of the substrate after the bacteria enters a logarithmic growth phase to satisfy specific formula.    USE - The method is useful for cultivating anaerobic ammonium-oxidizing bacteria capable of denitrifying ammonium and nitrate substrates (claimed) from nitrogen containing liquids such as waste water and aneorobically oxidizing ammonium and nitrite.    ADVANTAGE - The method provides for feeding of a substrate without waste to generate seed sludge with high bacterial cell concentration and start up operation within a short time, in cultivating anaerobic ammonium oxidizing bacteria with ammonium and nitrite as substrates, which allows a reduction in the cost of feeding the substrate as well as a significant reduction in the cost of treating waste liquids.    DETAILED DESCRIPTION - Cultivating anaerobic ammonium-oxidizing bacteria capable of denitrifying ammonium and nitrate substrates, involves cultivating the bacteria in a cultivation tank, feeding a substrate into the cultivation tank, and controlling a feed rate (Y) of the substrate after the bacteria enters a logarithmic growth phase to satisfy formula (I): Y=Axexp (KxT),    Y=feed rate of the substrate;    A=concentration of the substrate at the start of cultivation;    K=feed constant of the substrate; and    T=number of cultivation days after onset of the logarithmic growth phase.    An INDEPENDENT CLAIM is included for an equipment for cultivating anaerobic ammonium oxidizing bacteria capable of denitrifying ammonium and nitrite substrates, comprising:    (a) a cultivation tank for cultivating the bacteria;    (b) an ammonium feed device for feeding an ammonium substrate at a given concentration into the cultivation tank;    (c) a nitrite feed device for feeding a nitrite substrate at a given concentration into the cultivation tank; and    (d) a control device for controlling a feed rate (Y) of each of the substrates after the bacteria enters a logarithmic growth phase to satisfy formula (I).