An image reading apparatus that includes: an image sensor that outputs image signals in parallel from each block composed of an element group, photoelectric conversion elements arrayed in a main scanning direction being divided into the blocks; a serial transmission section that serializes and outputs the image signals outputted in parallel from the image sensor; a sampling section that samples the serialized image signals to add the blocks, to which the image signals belong, as block information to the respective image signals; a storage section that stores the image signals on the basis of a predetermined address; and a rearranging section that gives addresses for accessing to the storage section on the basis of the block information so that the image signals are arrayed from a head for the respective blocks in the main scanning direction of the image sensor, thereby to read/write the sampled image signals from/in the storage section.