An image reading apparatus, comprising: a driving unit configured to transmit a driving force; a conveyer unit configured to be driven by the driving force transmitted from the driving unit to convey sheets in a conveying direction along a conveyer path; an edge detecting sensor having an edge-contact piece and configured to detect front ends of the sheets conveyed along the conveyer path; and a reader unit configured to read images from the sheets being conveyed along the conveyer path, characterized by a separator unit configured to separate a plurality of stacked sheets one-by-one and convey the separated sheets along the conveyer path, wherein the conveyer unit is configured to convey the sheets separated by the separator unit in the conveying direction further along the conveyer path; a reducer unit, through which the driving force is transmitted to the conveyer unit and the separator unit; a size detecting unit configured to detect a size of the sheet prior to being conveyed by the conveyer unit; and a controller configured to control operations in the image reading apparatus including a conveying speed to convey the sheet, wherein the controller manipulates the conveyer unit via the driving unit to convey the sheet at a first conveying speed when the size of the sheet detected by the size detecting unit is greater than a predetermined size; and wherein the controller manipulates the conveyer unit via the driving unit to convey the sheet at a second conveying speed, which is lower than the first conveying speed, when the size of the sheet detected by the size detecting unit is one of smaller than and equivalent to the predetermined size. a driving unit configured to transmit a driving force; a conveyer unit configured to be driven by the driving force transmitted from the driving unit to convey sheets in a conveying direction along a conveyer path; an edge detecting sensor having an edge-contact piece and configured to detect front ends of the sheets conveyed along the conveyer path; and a reader unit configured to read images from the sheets being conveyed along the conveyer path, characterized by a separator unit configured to separate a plurality of stacked sheets one-by-one and convey the separated sheets along the conveyer path, wherein the conveyer unit is configured to convey the sheets separated by the separator unit in the conveying direction further along the conveyer path; a reducer unit, through which the driving force is transmitted to the conveyer unit and the separator unit; a size detecting unit configured to detect a size of the sheet prior to being conveyed by the conveyer unit; and a controller configured to control operations in the image reading apparatus including a conveying speed to convey the sheet, wherein the controller manipulates the conveyer unit via the driving unit to convey the sheet at a first conveying speed when the size of the sheet detected by the size detecting unit is greater than a predetermined size; and wherein the controller manipulates the conveyer unit via the driving unit to convey the sheet at a second conveying speed, which is lower than the first conveying speed, when the size of the sheet detected by the size detecting unit is one of smaller than and equivalent to the predetermined size.