An image reader including photoelectric transducers each of which converts a light signal into an electric signal, and outputs the signal to a signal line, channel selecting switches each of which selectively connects, and disconnects, a corresponding one of the transducers to, and from, the signal line, and a resolution selecting portion which receives a control-start signal which commands the image reader to start controlling the switches, and continues to take a predetermined voltage in a first predetermined time duration, and each one of clock-pulse signals which have respective different numbers of characteristic portions or portion in a second predetermined time duration falling in the first time duration, and each of which has pulses in a third time duration following the second time duration, the switches being sequentially controlled in synchronism with the pulses of the each clock-pulse signal, so as to sequentially connect, and disconnect, the corresponding transducers to, and from, the signal line, the resolution selecting portion selecting, based on the number of characteristic portions of the each clock-pulse signal, a corresponding one of different reading resolutions corresponding to different control patterns, respectively, so that the switches are sequentially controlled according to the control pattern corresponding to the selected reading resolution, in synchronism with the pulses of the each clock-pulse signal.