We present thermodynamic and neutron scattering data on silver ferrite AgFeO(2). The data imply that strong magnetic frustration Θ/T(N)∼10 and magnetic ordering arise via two successive phase transitions at T(2) = 7 K and T(1) = 16 K. At T<T(2), two metamagnetic phase transitions at B(1)∼14 T and B(2)∼30 T can be identified through the change of slope in the magnetization curve measured up to 53 T. These transitions roughly correspond to an eighth and a quarter of the saturation magnetizations. Unlike for the 'classical' delafossite CuFeO(2), the wavevector of the magnetic structure is independent of temperature both at T<T(2) and at T(2)<T<T(1).