An image reading apparatus for reading an image pattern of a detecting object comprises a detecting surface on which a detecting object is placed, a sensor array having a plurality of sensors arranged to read an image pattern of the detecting object placed on the detecting surface, a first detection electrode, provided on at least an upper portion of the sensor array, having the detecting surface; a second detection electrode provided to be electrically insulated and spaced from the first detection electrode; a counter electrode provided to be opposite to the first detection electrode through an interlayer insulating film; signal voltage applying circuit which applies a signal voltage having a first signal waveform that varies periodically to the counter electrode to excite a second signal waveform to the first detection electrode through the interlayer insulating film, and contact detector which determines whether the detecting object brought into contact with the detecting surface is a specific detecting object based on a third signal waveform excited to the second detection electrode according to contact of the detecting object with both the first detection electrode and the second electrode wherein a reading operation of the image pattern of the detecting object is performed based on the determination result by the contact detector.