The invention relates to the field of vehicle production line conveying, in particular to a tray automatic transferring device. The device comprises a lifting device and a conveying device, wherein the lifting device is used for transferring trays in the vertical direction, and the conveying device is used for transferring the trays in the horizontal transverse direction; the lifting device comprises a vertical column and a sliding frame, wherein the vertical column is vertically arranged, and the sliding frame can move up and down along the vertical column through a driving device; a tray lifting tool used for clamping the trays is arranged on the sliding frame; the conveying device comprises a guide rail which is horizontally transversely arranged, one end of the guide rail is fixed on anet rack platform, the other end of the guide rail extends to the position below the tray lifting tool when locating at the highest position of the vertical column in the horizontal transverse direction, and the guide rail is provided with a bearing device for transferring the trays along the guide rail. The device has the advantages that the structure is simple, the operation is convenient, thetransferring mode of the device is efficient and rapid, a large amount of transferring space is saved, and great popularization value is achieved.