An organic compound having a naphtho fluoranthene core and a hetero aromatic group bonded to a specific position of the naphtho fluoranthene core, an organic light-emitting diode and an organic light-emitting device including the compound are disclosed. Since the organic compound has a narrow Stokes Shift between an absorption wavelength and an emission wavelength, the organic compound has a broad overlapped area between its absorption peak and an emission peak of a delayed fluorescent material, and therefore it can emit blue light with high color purity. It is possible to manufacture an organic light-emitting diode (OLED) and an organic light-emitting device that enhance luminous efficiency and color purity using the organic compound.