An image processing device comprising: an image input unit which performs input of an image, the image including plural pixels arranged along a horizontal axis and a vertical axis orthogonal to each other; an edge direction detection unit which detects a direction of an edge of light and shade contained in the image inputted by the image input unit; and a first interpolation process unit which sets, as a first interpolation axis, a direction of the edge detected by the edge direction detection unit with respect to the input image inputted by the image input unit and performs an interpolation process for performing expansion/reduction of the input image along the first interpolation axis; and a magnification specification unit which designates magnification of expansion/reduction for the image inputted by the image input unit, wherein the first interpolation process unit includes: a first interpolation position decision unit which decides an interpolation position corresponding to the magnification designated by the magnification designation unit; and a first interpolation object pixel decision unit which extracts, as interpolation object pixels, n×n (n is an even number equal to or larger than four) pixels arranged around the interpolation position and along the direction of the edge detected by the edge direction detection unit, the first interpolation object pixel decision unit sets the first interpolation axis having the direction of the edge detected by the edge direction detection unit, and characterised in that the first interpolation process unit calculates pixel values in imaginary plural interpolation positions by performing the interpolation process along one interpolation axis of the first interpolation axis and a second interpolation axis and calculates, using pixel values corresponding to n interpolation positions obtained by the interpolation process, an interpolation value corresponding to the interpolation position, which is decided by the first interpolation position decision unit, along the other interpolation axis of the first and second interpolation axis, and the first interpolation object pixel decision unit sets, as the second interpolation axis, the horizontal axis or the vertical axis having an angle equal to or larger than 45 degrees with respect to the first interpolation axis. an image input unit which performs input of an image, the image including plural pixels arranged along a horizontal axis and a vertical axis orthogonal to each other; an edge direction detection unit which detects a direction of an edge of light and shade contained in the image inputted by the image input unit; and a first interpolation process unit which sets, as a first interpolation axis, a direction of the edge detected by the edge direction detection unit with respect to the input image inputted by the image input unit and performs an interpolation process for performing expansion/reduction of the input image along the first interpolation axis; and a magnification specification unit which designates magnification of expansion/reduction for the image inputted by the image input unit, wherein the first interpolation process unit includes: a first interpolation position decision unit which decides an interpolation position corresponding to the magnification designated by the magnification designation unit; and a first interpolation object pixel decision unit which extracts, as interpolation object pixels, n×n (n is an even number equal to or larger than four) pixels arranged around the interpolation position and along the direction of the edge detected by the edge direction detection unit, a first interpolation position decision unit which decides an interpolation position corresponding to the magnification designated by the magnification designation unit; and a first interpolation object pixel decision unit which extracts, as interpolation object pixels, n×n (n is an even number equal to or larger than four) pixels arranged around the interpolation position and along the direction of the edge detected by the edge direction detection unit, the first interpolation object pixel decision unit sets the first interpolation axis having the direction of the edge detected by the edge direction detection unit, and characterised in that the first interpolation process unit calculates pixel values in imaginary plural interpolation positions by performing the interpolation process along one interpolation axis of the first interpolation axis and a second interpolation axis and calculates, using pixel values corresponding to n interpolation positions obtained by the interpolation process, an interpolation value corresponding to the interpolation position, which is decided by the first interpolation position decision unit, along the other interpolation axis of the first and second interpolation axis, and the first interpolation object pixel decision unit sets, as the second interpolation axis, the horizontal axis or the vertical axis having an angle equal to or larger than 45 degrees with respect to the first interpolation axis.