In this paper, noise in resistive wall amplifier – vacuum microwave device is studied, in which in which the gain is due to the phase shift between the electron beam and the alternating field components due to the presence of absorbing walls. It should be noted that in resistive wall amplifier, there is no need for a slowing system and that almost completely there is completely lacks the feedback between the output and the input. Recently, attention has been paid to it, in particular, because of the possibility of using metamaterials that increase the gain factor.