looks like an A300 that has been modified as a freighter to transport sections of the A380 fuselage from wherever they are built to the Airbus assembly line in Toulouse

Boeing has a handful of 747s that serve a similar function on the 787 program (look up 747LCF, Dreamlifter)

edit Beluga has been used to ferry Airbus aircraft components between sites since 1995, as well as other outsize cargo on a charter basis ... it was initially built to replace the Super Guppy fleet (ex-NASA converted Boeing Stratocruisers)