Classical nova V339 Del (Nova Del 2013) is a fast nova of the Fe II class, whose eruption was ignited on a CO white dwarf (WD). In this contribution we present the spectral energy distribution (SED) of the nova optical spectrum throughout its main stages of evolution: The fireball stage, transition to a harder spectrum, super-soft X-ray source phase and the nebular phase. We achieved this aim by the method of multiwavelength modelling the SED. During the fireball stage the nova spectrum was well comparable with the atmospheric models for a star of spectral type A. During two days following the fireball stage, the maximum of the WD radiation shifted out-of the optical to shorter wavelengths and a strong nebular continuum emerged and modulated considerably the whole optical to near-IR. The super-soft X-ray source phase was characterized with a flat optical continuum determined by the nebular emission. During the nebular phase, the optical spectrum was steep towards the short wavelengths reflecting a dominant contribution from the cooling WD photosphere, whereas the nebular continuum decreased by a factor of ~30 with respect to the super-soft source phase. Our analysis confirmed that V339 Del is an extraordinary nova.