A centering mechanism comprising: a centering unit configured to convey a paper sheet in a pinched state, and center a position of the paper sheet in a width direction orthogonal to a conveyance direction of the paper sheet by inclining with respect to the conveyance direction; an upstream side conveyance unit that is arranged on an upstream side of the centering unit in the conveyance direction set when the centering unit centers a position of the paper sheet in the width direction, and is configured to convey the paper sheet; and a downstream side conveyance unit that is arranged on a downstream side of the centering unit in the conveyance direction set when the centering unit centers a position of the paper sheet in the width direction, and is configured to convey the paper sheet in a pinched state, wherein the paper sheet is delivered to the downstream side conveyance unit from the centering unit in a state in which the centering unit pinches the paper sheet, and the downstream side conveyance unit conveys the paper sheet while pinching the paper sheet at pinch pressure stronger than pinch pressure at which the centering unit pinches the paper sheet, characterised in that: the centering mechanism further comprises a plurality of the centering units arrayed in the width direction, wherein each of the plurality of centering units includes: a conveyance roller; a first gear provided on a rotational shaft of the conveyance roller; and a second gear configured to engage with the first gear, and rotate around a swing center around which the centering unit swings in such a manner as to incline with respect to the conveyance direction, and wherein the centering mechanism includes: a third gear provided on a rotational shaft of the upstream side conveyance unit or the downstream side conveyance unit; a fourth gear configured to engage with the third gear, and rotate around a rotational center parallel to the swing center of the centering unit; and a plurality of second power transmission units connected to the fourth gear and a plurality of the second gears. a centering unit configured to convey a paper sheet in a pinched state, and center a position of the paper sheet in a width direction orthogonal to a conveyance direction of the paper sheet by inclining with respect to the conveyance direction; an upstream side conveyance unit that is arranged on an upstream side of the centering unit in the conveyance direction set when the centering unit centers a position of the paper sheet in the width direction, and is configured to convey the paper sheet; and a downstream side conveyance unit that is arranged on a downstream side of the centering unit in the conveyance direction set when the centering unit centers a position of the paper sheet in the width direction, and is configured to convey the paper sheet in a pinched state, wherein the paper sheet is delivered to the downstream side conveyance unit from the centering unit in a state in which the centering unit pinches the paper sheet, and the downstream side conveyance unit conveys the paper sheet while pinching the paper sheet at pinch pressure stronger than pinch pressure at which the centering unit pinches the paper sheet, characterised in that: the centering mechanism further comprises a plurality of the centering units arrayed in the width direction, wherein each of the plurality of centering units includes: a conveyance roller; a first gear provided on a rotational shaft of the conveyance roller; and a second gear configured to engage with the first gear, and rotate around a swing center around which the centering unit swings in such a manner as to incline with respect to the conveyance direction, and wherein the centering mechanism includes: a third gear provided on a rotational shaft of the upstream side conveyance unit or the downstream side conveyance unit; a fourth gear configured to engage with the third gear, and rotate around a rotational center parallel to the swing center of the centering unit; and a plurality of second power transmission units connected to the fourth gear and a plurality of the second gears. a conveyance roller; a first gear provided on a rotational shaft of the conveyance roller; and a second gear configured to engage with the first gear, and rotate around a swing center around which the centering unit swings in such a manner as to incline with respect to the conveyance direction, and wherein the centering mechanism includes: a third gear provided on a rotational shaft of the upstream side conveyance unit or the downstream side conveyance unit; a fourth gear configured to engage with the third gear, and rotate around a rotational center parallel to the swing center of the centering unit; and a plurality of second power transmission units connected to the fourth gear and a plurality of the second gears. a third gear provided on a rotational shaft of the upstream side conveyance unit or the downstream side conveyance unit; a fourth gear configured to engage with the third gear, and rotate around a rotational center parallel to the swing center of the centering unit; and a plurality of second power transmission units connected to the fourth gear and a plurality of the second gears.