An image processing apparatus includes a sensor unit configured to include a plurality of line sensors to read image data having a plurality of channels; a correcting unit configured to correct the image data read by the sensor unit to obtain a plurality of frames of image data in which reading positions on an original image by adjacent line sensors among the plurality of line sensors are shifted by less than a pixel in a main scanning direction or/and a sub-scanning direction; and a high-resolution converting unit configured to perform interpolation by using the plurality of frames of image data obtained by the correcting unit so as to obtain monochrome image data having resolution higher than resolution of the line sensors.