The present invention relates to a ski boot (1), of the type comprising a substantially soft inner liner, a substantially rigid outer shell (3) and a cuff (5) articulated to said shell, and further comprising a spoiler (9) articulated to said shell and arranged between said inner liner and said cuff. The ski boot according to the invention comprises a locking device (11) for selectively allowing or preventing rotation of said cuff (5) relative to said shell (3) and, at the same time, for selectively allowing or preventing the movements of said spoiler (9) relative to said cuff (5), and consequently also relative to said shell (3).