1. An image processing apparatus for correcting a defective portion in image data having a plurality of pixels, the apparatus comprising: a target pixel selecting section for selecting one target pixel from a plurality of defective pixels included in the image data; a normal pixel searching/detecting section for searching/detecting one or more normal pixels on each of opposed sides across the target pixel along each of a plurality of search lines extending through the target pixel; a searching-interval adjusting section for adjusting a searching interval on each search line along which the normal pixel detecting section searches and detects the normal pixels, depending on the number of pixels included in the image data; an interpolation value calculating section for calculating an interpolation value for said target pixel for each said search line, based on pixel values of the normal pixels detected by the normal pixel searching/detecting section along that search line; a weight coefficient calculating section for calculating a weight coefficient for each said search line, based on the pixel values of the normal pixels detected by the normal-pixel searching/detecting section; a weighted average value calculating section for calculating a weighted average value for said target pixel, based on said interpolation value and said weight coefficient for said target pixel for each said search line; and a correcting section for correcting said target pixel by using said weighted average value calculated by said weighted average value calculating section.