Missing-pixel interpolation data are obtained such that the mean value of a plurality of pixels constituting a group of pixels including a missing pixel is equal to the mean value of a plurality of pixels constituting a group of pixels not including the missing pixel. For example, missing-pixel interpolation data are obtained by (1) obtaining a sum (SL) of the values of pixels other than the missing pixel (L) in the k pixels constituting the group (LC) of pixels including the missing pixel, (2) obtaining a sum (SA) of the values of k pixels constituting a group (NA) of pixels not including the missing pixel, and (3) taking the difference between these sums. This makes it possible to reduce interpolation error when a highly periodic image with missing pixels is interpolated.