To speedily carry out lot change by properly storing unrequired empty trays produced on a carrier passage as required and to most suitably adjust the number of the trays in accordance with a yarn number count, winding speed, etc.

A tray storage device 15 to store a plurality of empty trays by piling them up in stages is arranged in the middle of an empty tray carrier passage 19 in a bobbin treatment part 12 on a tray carrier system to supply a bobbin to an automatic winder constituted by providing a plurality of winding units in parallel. The tray storage device 15 works when it detects that no bobbin for installation in a bobbin installation device 16 is left and stores all trays of specific kinds carried on the empty tray carrier passage 19.