The instant invention relates to an apparatus for measuring a powder mass flow in a powder/gas mixture during the conveyance thereof through a feed pipe, the apparatus comprising a velocity measuring device for the powder/gas mixture, a mass measuring device for the powder mass per volume unit, and a calculating device to calculate the powder mass flow based on the velocity measured, the powder mass per volume unit measured, and the dimensions of the feed pipe. The mass measuring device comprises a microwave resonator and means for sensing the resonant frequency and/or the microwave amplitude of the microwave resonator. The microwave resonator is embodied by a coil which is applied on the outside of the feed pipe. The invention likewise proposes a method of measuring the powder mass flow in a feed pipe wherein measuring of the powder mass per volume unit involves establishing a reference resonance of a known powder mass flow, adjusting two measuring frequencies at either side of the reference resonance, measuring the resonator voltage at the adjusted measuring frequencies and forming the difference thereof for a powder mass flow to be measured, and determining the displacement of the resonant frequency based on the voltage differential.