An interpolation processing section determines a pixel value of an interpolation-target pixel by a diagonal interpolation process. An interpolation value limiting section compensates the pixel value determined by the interpolation processing section such that it becomes a value between pixel values of two adjacent pixels above and below the interpolation-target pixel. An intersection area detecting section judges whether or not the interpolation-target pixel is located in, when the horizontal axis represents a horizontal position and the vertical axis represents a pixel value, an area in proximity of a horizontal position where a curve line, representing pixel values of pixels on the scanning line above the interpolation-target pixel, and a curve line, representing pixel values of pixels on the scanning line below the interpolation-target pixel, intersects. Depending on a judgment result by the intersection area detecting section, a selecting section selectively outputs a pixel value determined by the interpolation processing section, or a pixel value compensated by the interpolation value limiting section, as an interpolated video signal. By this, the advantageous effect of the diagonal interpolation process is fully exerted while suppressing image quality degradation due to a false operation of the diagonal interpolation process.