PURPOSE: To transport sheets without causing buckling even in those with low toughness in a system in which sheets are discriminated while transported by a two-belt conveyor by furnishing a discriminating swing piece at the part two belts go apart and thereby forming an air flow in the gaps between the sheet and the belts.

CONSTITUTION: When a sheet 6 is sent into the transport line 9 constituted by a belt 1 and a belt 3, the tip of a swing piece 5 is swung toward a guide pulley 11 so that the sheet 6 runs further between the swing piece 5 and belt 1. At this time, air blown out of a nozzle 15 forms an air flow 17 in said gap 16, so that frictional resistance is extremely small and thereby the sheet is discriminated without risk of buckling and sent to the transport line 9 smoothly.