We study magnetism of an adatom adsorbed on AA-stacked bilayer graphene (BLG) in both unbiased and biased cases, using the Anderson impurity model. We find different magnetic phase diagrams for the adatom, depending on the energy level of the adatom, which varies from the magnetic phase diagram of adatom in normal metals to that in graphene. This is due to the individual energy dependence of the density of states (DOS) of AA-stacked BLG and anomalous broadening of the adatom energy level. Furthermore we investigate the effect of a bias voltage on DOS of AA-stacked and show that the magnetization of the adatom can be controlled by applying the bias voltage. This allows for possibility of using AA-stacked BLG in spintronic devices.