A driving section 4 supplies a reading pulse of ‘H’ to electrodes V1 and V5 simultaneously with completion of exposure to read out electric charges to empty packets below electrodes V1, V2, V5, and V6. Then, the driving section 4 supplies a driving pulse of ‘M’ to electrodes V3 and V7 and a multiplication pulse to the electrodes V2 and V6. At this time, a level of the multiplication pulse supplied to the electrodes V2 and V6 is set so that a potential difference between the electrodes V1 and V3 and the electrode V2 and a potential difference between the electrodes V5 and V7 and the electrode V6 become values required to cause avalanche multiplication. Electric charges accumulated below the electrodes V1 to V3 move into packets formed below the electrodes V2 and V6. The avalanche multiplication occurs at the time of movement. Thus, the electric charges are multiplied.