Abstract: An unstacking feeder capable of unstacking sheet materials efficiently from a sheet stack has a sheet stack transfer device (3) for transferring a sheet stack, which consists of a plurality of stacked sheet materials (1a), along a circulating transport configuration extending across a predetermined unstacking position (A). In order to separate individual sheet materials from a sheet stack in order, a floater (6) is selected and supplied automatically in accordance with the configuration of the sheet materials by a floater supply mechanism (5, 7, 7d). Each unstacked sheet material is transferred to equipment in the subsequent stage, such as a transfer feeder by sheet material transporting arrangements (11, 19). During this period, each sheet material (1a) separated by the floater (6) is transferred onto a sheet material transporting arrangement by a sheet material transfer device (9).