A sheet conveying device conveys sheets by using a suction conveyor belt having small holes. The lowermost sheet stacked on a sheet table is conveyed while being adsorbed on the conveyer belt. A suction fan sucks the lowermost sheet by way of an air suction port formed in a suction duct and the small holes. Sucked air is introduced into an air nozzle through a guide duct. Air blown off from the air nozzle raises the second sheet from the lowermost sheet and the subsequent sheets, to separate the sheets from the lowermost sheet. The suction duct is provided with an auxiliary suction port for ensuring the amount of air blown off from the air nozzle.