An image reader includes an original transport device to transport an original, and an image reading device including multiple image sensor arrays having image reading areas staggered relative to the transport direction of the original in such a manner that the multiple image sensor arrays are offset at least partially, in the main scanning direction of the original with a predetermined gap therebetween in the transport direction. There is at least one original transport speed detector to detect the transport speed of the original transported by the original transport device, a storing device to store a reference delay time period which is between when the image sensor arrays on the upstream side read a predetermined position relative to the transport direction and when the image sensor arrays on the downstream side read the predetermined position. Further, there is a misalignment amount calculator, and an image synthesizer to synthesize an image read by the image sensor arrays.