The need for highly efficient devices with longer operating lives in the blue wavelength region is increasing. Herein, we showed that hexagonal boron nitride, as a blue luminescent material, is promising because it is a wide bandgap semiconductor with very high thermal and chemical stabilities and can be used in devices operating under extreme conditions. Specifically, through the highly luminous properties of exfoliated hexagonal boron nitride (Exf-hBN), a blue emission device equipped with a field-emission array using carbon nanotube as an excitation source was fabricated and its stable operation has been demonstrated. Furthermore, the cathodoluminescent device is thinner than conventional lamps when using the ultra-thin Exf-hBN film and graphene as an electrode. The blue fluorescence of Exf-hBN may allow new devices to be developed with extraordinary properties for applications from optoelectronics to biotechnological devices.