An image sensor having an photodetecting element array including a plurality of blocks linearly arrayed in a main scan direction, each block consisting of a plurality of photodetecting elements, a plurality of switching elements for transferring every block charges generated in the photodetecting elements, and drive ICs for outputting the charges in the form of image signals. In the image sensor, the switching elements in a block of the photodetecting element array and the switching elements in another block located adjacent to the former block are connected by wires in such a way that the switching elements closest to each other between the blocks are interconnected, the switching elements next close to each other are interconnected, and so on. The wires connecting from the switching elements in a block to the switching elements in blocks on both sides of the former block are disposed oppositely with respect to the main scan direction, and are disposed in such a way that the shortest wire connecting the switching elements is located closest to the photodetecting element array, the next short wire is located next close to the photodetecting element array, and so on.