A double-sided glassless three-dimensional (3D) display apparatus including a backlight unit may include an light source unit configured to emit light to the front and the rear thereof by diffracting incident light, and first and second display devices configured to use the light emitted by the light source unit as light for a 3D image formation and to form the 3D image on both sides of the light source unit. The light source unit may include a light source portion configured to emit three lights that have three different respective wavelengths and a light guide panel configured to transmit the lights emitted by the light source portion to the first and second display devices.