The invention relates to an autonomous apparatus for the photo-polymerization of a flexographic printing plate, which plate comprises a main face and a base opposite to said main face. The apparatus comprises an exposure chamber in which at least first photo-polymerization means of said base of said plate are installed. An input section and an output section are defined for letting said plate into/out from the exposure chamber, respectively. The apparatus further comprises moving means configured to drag said plate along a feeding direction. According to the invention, the first photo-polymerization means comprise a row of LEDs aligned according to a direction substantially orthogonal to said feeding direction.