An image reader of the present invention comprises a fluctuation detector that can be connected to the external equipment by means of an image data input-output section, and can subject image data, continuous in a first direction and outputted as image information on a test chart is photoelectrically converted by means of a CCD sensor when a mirror set or the test chart is moved in the first direction, to Fourier conversion, thereby obtaining the frequency of a fluctuation of the obtained image data and a maximum value of the amplitude thereof. If the obtained maximum value of the fluctuation amplitude is greater than a given value, the fluctuation detector is used to compare the frequency of the fluctuation and the natural frequency of a drive motor for generating driving force for moving the mirror set or the image. If the fluctuation frequency and the natural frequency are not equal, the value of current supplied to the drive motor is increased.