PURPOSE: To prevent fluctuation in read accuracy and a picture signal level by extracting a picture signal by one line from an image sensor for each input of an input signal synchronously with a highest relative speed between the image sensor and a medium from an external device.

CONSTITUTION: A control logic section 13 receives a medium carrier pulse STP from an external controller 12 and drives a CCD 14 with a clock CLK with a prescribed period and a scan start pulse ISTP with a prescribed period. The CCD 14 implements picture reading by one line each for each trailing of the ISTP and outputs a picture signal one by one line. Furthermore, the period of the ISTP is set to a period corresponding to the maximum value of a card carrying speed. An A/D converter section 16 A/D-converts a picture signal from an analog signal processing section 15 based on a clock from a logic section 13 and a power supply from the converter 16 is written in an FIFO memory 17 by plural bits each with a write signal/W. Thus, the fluctuation in the read accuracy and a picture signal level is prevented.