A display apparatus for a mixed reality environment includes an image processor for mixing an actual image of an object around a user and a artificial stereo images to produce multiple external image signals, a user information extractor for extracting the user's sight line information including the user's position his/her eye position, direction of a sight line and focal distance; an image creator for creating a stereo image signal based on the extracted user's sight line information; an image mixer for synchronously mixing the multiple external image signals and the stereo image signal; and an image output unit for outputting the mixed image signal to the user.