A duplex scanning apparatus and a sheet-feeding control method thereof are provided. The duplex scanning apparatus includes a sheet feeding channel, a sheet transfer channel, an inverting channel, and a sheet sensing module. A first end of the inverting channel is connected to a junction between said sheet feeding channel and the sheet transfer channel. A second end of the inverting channel is connected to the sheet transfer channel. A distance between the sheet sensing module and the first end of the inverting channel is greater than a distance between the sheet sensing module and the second end of the inverting channel. When a document is transferred through the sheet sensing module at the second time, a next document is fed into the sheet feeding channel through a sheet entrance.