An image processing device includes a computer that is configured to: perform order-statistic filter processing on pixel values of individual pixels in a block including a pixel of interest and peripheral pixels in an acquired image; calculate a difference value between the pixel values of the pixel of interest before and after the order-statistic filter processing is performed; calculate a statistical variation of the pixel values of the peripheral pixels subjected to the order-statistic filter processing; and determine the pixel of interest as being a defective pixel in the case where a value obtained by dividing the difference value by the statistical variation is greater than or equal to a predetermined threshold.