An image processing apparatus comprising a distortion correcting means and a distortion correcting range calculating unit, the distortion correcting range calculating unit being configured to calculate an input image range for distortion correction processing performed by the distortion correcting means, the distortion correcting means being configured to correct distortions sequentially in units of block lines, a block line being small image region of the input image, in accordance with input image ranges calculated by the distortion correcting range calculating unit; wherein the distortion correcting range calculating unit comprises: a coordinate generating unit adapted to generate interpolation coordinates corresponding to coordinates of a plurality of positions (X, Y) of the corrected image; a distortion-correction coordinate transforming unit adapted to output transformed coordinates of a plurality of positions (X', Y') of the input image corresponding to the coordinates of the plurality of positions (X, Y) of the corrected image by applying in accordance with a predetermined distortion correcting formula distortion correction coefficients (A, B, C,...) to a distance denoting the distance between a distortion center (X d, Y d) and the corrected points (X, Y), said distance being calculated from the coordinates (X, Y) of positions of the corrected points, coordinates (X d, Y d) of the distortion center, corrected values (X off, Y off) of a central deviation in the corrected image, and a sampling ratio (S x, S y) in a longitudinal direction and a lateral direction of the corrected image, and having higher-degree exponents in the distortion-correction formula; and a correcting range detecting unit adapted to calculate, from the transformed coordinates of the plurality of positions, a range of the input image for distortion correction processing performed by the distortion correcting means using the transformed coordinates (X', Y') of the plurality of positions of the input image, wherein the correcting range detecting unit of the distortion correcting range calculating unit is configured to calculate simultaneously, during the execution of the distortion correction processing on a sequentially preceding block line by the distortion correcting means, a distortion correction range for distortion correction processing of a next block line different from said preceding block line based on the transformed coordinates of the positions (X', Y') of the input image calculated by the distortion-correction coordinate transforming unit, such that upon ending distortion correction of a block line, the input image range for distortion correction of the next block line is known and can be sequentially and smoothly performed without delay. a coordinate generating unit adapted to generate interpolation coordinates corresponding to coordinates of a plurality of positions (X, Y) of the corrected image; a distortion-correction coordinate transforming unit adapted to output transformed coordinates of a plurality of positions (X', Y') of the input image corresponding to the coordinates of the plurality of positions (X, Y) of the corrected image by applying in accordance with a predetermined distortion correcting formula distortion correction coefficients (A, B, C,...) to a distance denoting the distance between a distortion center (X d, Y d) and the corrected points (X, Y), said distance being calculated from the coordinates (X, Y) of positions of the corrected points, coordinates (X d, Y d) of the distortion center, corrected values (X off, Y off) of a central deviation in the corrected image, and a sampling ratio (S x, S y) in a longitudinal direction and a lateral direction of the corrected image, and having higher-degree exponents in the distortion-correction formula; and a correcting range detecting unit adapted to calculate, from the transformed coordinates of the plurality of positions, a range of the input image for distortion correction processing performed by the distortion correcting means using the transformed coordinates (X', Y') of the plurality of positions of the input image, wherein the correcting range detecting unit of the distortion correcting range calculating unit is configured to calculate simultaneously, during the execution of the distortion correction processing on a sequentially preceding block line by the distortion correcting means, a distortion correction range for distortion correction processing of a next block line different from said preceding block line based on the transformed coordinates of the positions (X', Y') of the input image calculated by the distortion-correction coordinate transforming unit, such that upon ending distortion correction of a block line, the input image range for distortion correction of the next block line is known and can be sequentially and smoothly performed without delay.