The present disclosure relates to a thin film type controlled viewing window back light unit and a thin flat type Controlled Viewing window Display using the same. The present disclosure suggests a thin film type back light unit which can include: a base film having a width and a length, and including a high refractive film and a low refractive film stacked on the high refractive film; an incident pattern disposed at one side of a bottom surface of the base film; a reflective pattern disposed at an opposite side apart from the one side with the length of the bottom surface of the base film, and covering the width of the opposite side; a light radiating pattern disposed on an upper surface of the base film; a holographic film for controlling a viewing-window disposed on the light radiating pattern; and a light source being apart from the incident pattern, and providing an incident light to the incident pattern.