In one embodiment, image reading apparatuses 100a and 100b start reading an original image after a reading start time Ta has elapsed since detecting the transport timing of an original G on the upstream side in a transport direction Y1 relative to an original reading position R1, adjust the reading start time Ta based on a reading timing adjustment time T1a from when the transport timing of an adjustment sheet P is detected until when original reading portions 200a and 200b read a position considered to be a leading edge P′ in a first mark Q1 on the adjustment sheet P, and correct the reading start timing of the original G based on a leading edge reading error correction time T2a stored in advance.