Disclosed are a method and apparatus for replacing missing image data. The method of replacing missing image data includes receiving input image data for at least two or more domains among preset multiple domains, and restoring missing image data of a preset target domain by using a neural network that uses the two or more input image data as inputs. The neural network may combine fake image data of a first target domain generated by inputting real image data of at least two or more domains of the multiple domains and the real image data, and be trained by using a multi-cycle consistency loss in which an image restored by inputting the combined image data is similar with the real image data.