PURPOSE: To vary the height of a tray inlet by making a coupled chain having partially grooves engaging tray pins surround and engage three sprockets disposed in the three directions on the vertical plane and changing the shaft positions of at least two sprockets.

CONSTITUTION: Stacked trays 1 are held on a support bed 45 vertically movably through a bracket section 45A. A tray inlet holding member is supported by the side walls 46 of frame and the position of shaft of a drive sprocket 31A among three sprockets is fixed. The shafts of driven sprockets 31B, 31C are movably fitted in slots provided in the side walls to change their positions. The three sprockets 31AW31C are surrounded by a coupled chain 32 having partiallly grooves 35 engaging tray pins. Thus, by vertically moving the position of driven sprocket 31B is changed vertically the position of groove 35 of the coupled chain 32 engaging the tray pin to vary the height of inlet.