A method and apparatus for generating a thumbnail image are provided so that the out-of-focus (OOF) information can be ascertained from looking at the thumbnail. An input image is decoded, and a degree of the amount of OOF of the decoded image is measured (OOF information). There is a determination as to whether or not there is an EXchangeable Image File (EXIF) information about the input image. In the presence of EXIF information, a thumbnail image is extracted from the EXIF information and as much an OOF effect is applied to the thumbnail image in accordance with the degree of OOF. In the absence of the EXIF information, a thumbnail image is generated by scaling down the decoded image at a down scaler and applying as much of an OOF effect is applied to the thumbnail image in accordance with the degree of OOF.