PURPOSE: To automatically convey sheets of paper, divisionally collected on the basis of divisional information to a collecting box group vertically arranged in plural stages, to the next process at each collecting box.

CONSTITUTION: If a suitable quantity of mail A... is collected to each collecting box 5aW5d in a sorter main unit 1, mail A'... are transferred to empty trays 16... in horizontal conveying tray paths 17aW17d of the first conveying mechanism 8. The tray in the tray horizontal conveying path is moved pitch by pitch, transferred respectively to confluent connection conveying paths 18aW18d in a confluent mechanism 10, and arranged to the same position as the tray 16 of the confluent connection conveying path 18d by lowering action of a lowering elevator, and these trays 16... are fed into a confluent conveying path 20, then the main A is transferred to a locking pin line 21 by a mail transfer device 22. The empty trays 16... are returned to a start end side of the tray horizontal conveying path.