An image reading apparatus includes a reading unit that has multiple pixels for performing image reading, a driving unit that outputs a driving signal to the pixels of the reading unit, and a connection unit that connects the reading unit to the main body of the image reading apparatus. An identification signal is inserted by the driving unit at a specific pixel among ineffective pixels that do not react to external light among the pixels of the reading unit, and detection of whether or not the reading unit is connected correctly to the main body of the image reading apparatus by the connection unit is performed by examining the signal level of the specific pixel.