In a printing system capable of selectively performing duplex printing and simplex printing, a first input unit and a second input unit are adjacent to each other. A first output unit and a second output unit are adjacent to each other. In duplex printing, a sheet supplied from the first input unit is printed on a first side thereof in a first printing apparatus and the traveling direction thereof is changed at a changing unit while the sheet is reversed, and then the sheet is printed on a second side thereof in a second printing apparatus and output to the second output unit. In simplex printing, a sheet supplied from the first or second input unit is printed on one side thereof and the traveling direction thereof is changed at the changing unit, and then the sheet is output to the first or second output unit.