A scanner that combines images read by a first sensor array (21a1) and a second sensor array (21a2), wherein the first sensor array and the second sensor array have read regions which are overlapped partially, and the scanner comprises: a processor that combines and outputs an image of a straight line present in a region of a document that is read by the first sensor array and the second sensor array, wherein the straight line is neither parallel nor perpendicular to a main scanning direction of the scanner, and the image output by the processor comprises a non-straight line as a processed image of the straight line, characterized in that the processor combines and outputs the image such that a single line is drawn as a representation of the straight line that is neither parallel nor perpendicular to a main scanning direction in a case where the document is shifted in a direction perpendicular to the document from a reference position by an amount such that reading results of the first sensor array and the second sensor array are deviated by at least four pixels in the main scanning direction compared to the read results that would be obtained were the document to be located at the reference position, and the straight line which is neither parallel nor perpendicular to the main scanning direction is read by the first sensor array and the second sensor array as an image having a width of two pixels in the main scanning direction, wherein the processor combines and outputs the image in which the non-straight line is drawn such that a centre portion of the non-straight line has an angle closer to the main scanning direction than the straight line on the document, the centre portion being an oblique line neither parallel nor perpendicular to the main scanning direction. wherein the first sensor array and the second sensor array have read regions which are overlapped partially, and the scanner comprises: a processor that combines and outputs an image of a straight line present in a region of a document that is read by the first sensor array and the second sensor array, wherein the straight line is neither parallel nor perpendicular to a main scanning direction of the scanner, and the image output by the processor comprises a non-straight line as a processed image of the straight line, characterized in that the processor combines and outputs the image such that a single line is drawn as a representation of the straight line that is neither parallel nor perpendicular to a main scanning direction in a case where the document is shifted in a direction perpendicular to the document from a reference position by an amount such that reading results of the first sensor array and the second sensor array are deviated by at least four pixels in the main scanning direction compared to the read results that would be obtained were the document to be located at the reference position, and the straight line which is neither parallel nor perpendicular to the main scanning direction is read by the first sensor array and the second sensor array as an image having a width of two pixels in the main scanning direction, wherein the processor combines and outputs the image in which the non-straight line is drawn such that a centre portion of the non-straight line has an angle closer to the main scanning direction than the straight line on the document, the centre portion being an oblique line neither parallel nor perpendicular to the main scanning direction. a processor that combines and outputs an image of a straight line present in a region of a document that is read by the first sensor array and the second sensor array, wherein the straight line is neither parallel nor perpendicular to a main scanning direction of the scanner, and the image output by the processor comprises a non-straight line as a processed image of the straight line, characterized in that the processor combines and outputs the image such that a single line is drawn as a representation of the straight line that is neither parallel nor perpendicular to a main scanning direction in a case where the document is shifted in a direction perpendicular to the document from a reference position by an amount such that reading results of the first sensor array and the second sensor array are deviated by at least four pixels in the main scanning direction compared to the read results that would be obtained were the document to be located at the reference position, and the straight line which is neither parallel nor perpendicular to the main scanning direction is read by the first sensor array and the second sensor array as an image having a width of two pixels in the main scanning direction, wherein the processor combines and outputs the image in which the non-straight line is drawn such that a centre portion of the non-straight line has an angle closer to the main scanning direction than the straight line on the document, the centre portion being an oblique line neither parallel nor perpendicular to the main scanning direction.