The invention relates to a supply device (1) for a screening machine (2), having a conveying channel (10) with a channel bottom (11), a feed region (15) and an ejection edge (14), and also a vibration transducer system (20) coupled to the conveying channel (10). The supply device (1) is characterized in that vibrations of the conveying channel (10) that are induced by the vibration transducer system (20) have components in the longitudinal direction (x) and in the transverse direction (y) of the channel bottom (11) and also in a direction (z) perpendicular to the channel bottom (11), wherein the components are phase-shifted with respect to one another in the longitudinal direction (x) and transverse direction (y).