In a sheet conveying device, a foreign substance separating unit (50) has an air discharge chamber (56), foreign substance collection chamber (57),air introduction chamber (55), a plurality of first air vents (58a) formed in a first partition wall (58) that partitions the air introduction chamber (55) and the foreign substance collection chamber (57), a plurality of second air vents (60a) formed in a second partition wall (60) that partitions the air introduction chamber (56) and the air discharge chamber (56), centrifugal separation parts (59) each including a reverse truncated cone-like wall portion extending downward from each of the first air vents (58a), cylindrical parts (61) that each are provided coaxially with each of the centrifugal separation parts (59), and an inclination surface portion (62a) that is formed around each of the cylindrical parts (61) above each of the first air vents (58a) and is inclined in a circumferential direction.