A 3-dimensional (3D) holographic image displaying apparatus is provided. The apparatus includes a hologram reproducer configured to generate surface plasmons in response to incident light and reproduce a 3D image by diffracting the generated surface plasmons by a hologram, and a surface light source unit including a light source and a light guide plate, the light guide plate being configured to allow incident light from the light source to enter into the light guide plate, internally reflect the allowed light, and output the internally reflected light through a light-output surface, the surface light source unit being configured to implement colors by adjusting an angle of the light incident to the hologram reproducer so that the outputted light through the light-output surface is incident to the hologram reproducer at a surface plasmon-forming angle for each wavelength to generate the surface plasmons corresponding to a plurality of color beams.