A sheet feeder including a fixed gate (4) provided on a base (11) and approximately orthogonal to the direction of feed of sheets, and a movable guide plate (41) provided on the base (1) in parallel to the fixed gate movably toward and away from the fixed gate and positionable in place. The feeder kicks out thick sheets (S) stacked up between the gate (4) and the guide plate (41) one by one from the lowermost position by a suction device (2) and a kicker (10). The feeder comprises guide members (11) arranged side by side above the base (1) and orthogonal to the gate (4), a slide member (21) integral with the guide plate (41) and disposed over the guide members (11) thereacross movably toward and away from the gate (4), and belts each provided on its surface with a kicker member (31) for engaging one end of the sheet and revolvably disposed within a belt support. The belt support is disposed between adjacent guide members, attached to the slide member (21) and communicates with the suction device (2). The sheets can be kicked out one by one by the kicker member (31) on each belt (3) which is driven in revolution in a specified position, with suction applied at least locally on the lower surface of the sheet.