1. A scanner having a two-linear image sensor, which comprises a linear image sensor for the color green in which a plurality of photo elements corresponding to pixels are arranged in a row and filters which allow transmission of a green light component are provided on the light-receiving surfaces of the photo elements so that the sensor will output a green image signal representing an image of interest, and a linear image sensor for both the colors red and blue in which a plurality of photo elements corresponding to pixels are arranged in a row and in parallel with the linear image sensor for the color green and filters which allow transmission of a red light component and filters which allow transmission of a blue light component are alternately provided on the light-receiving surfaces of the photo elements so that the sensor will output a red image signal and a blue image signal representing an image of interest, and a conveyance device for conveying the image of interest and the two-linear image sensor relative to each other, said scanner comprising: a red-color average signal calculating circuit for calculating the average of pixel signals represented by the red image signals present on both sides of a red-color interpolation target pixel, which is a portion at which a pixel represented by the red image signal is missing, this pixel being one corresponding to a pixel represented by the green image signal; a red-color interpolation target pixel correcting circuit for correcting the average signal calculated by said red-color average signal calculating circuit; a blue-color average signal calculating device for calculating the average of pixel signals represented by the blue color image signals present on both sides of a blue-color interpolation target pixel, which is a portion at which a pixel represented by the blue image signal is missing, this pixel being one corresponding to a pixel represented by the green image signal; and a blue-color interpolation target pixel correcting device for correcting the average signal calculated by said blue-color average signal calculating circuit.