There are provided a first intermediate image generating means (1) for generating a first intermediate image (D1) by extracting a component in a vicinity of a particular frequency band in an input image (DIN), a second intermediate image generating means (2) for generating a second intermediate image (D2) from the first intermediate image (D1), and an adding means for adding the input image (DIN) and the second intermediate image (D2). The second intermediate image generating means (2) includes a non-linear processing means (2A) that varies the content of its processing according to the pixel in the intermediate image (D1). Even if the input image includes a fold-over component on the high-frequency side or does not include an adequate high-frequency component, adequate image enhancement processing can be carried out.