An image reader in which a plurality of light-sensitive cells arranged in an array in a line image sensor are divided into a predetermined number of blocks, and the blocks are sequentially selected to sequentially drive the light-sensitive cells in each of the blocks to produce image signals. Charging switches are provided for charging the light-sensitive cells via block selector switches. The charging switches are activated after a signal read time assigned to each light-sensitive cell has expired to thereby shorten the charging time necessary for the light-sensitive cell. The block selector switches are each actuated at a predetermined timing while the charging switches are activated, thereby preventing noise due to switching actions of the block selector switches from being introduced into image signals.