A C-axis unit for a machine tool, the C-axis unit comprising a bushing (134) adapted to be fixed to a unit support (121) of the machine tool; a head mounting platform (130) adapted to receive an operating head (40), the head mounting platform being supported by the bushing (134) and being rotatable relative to the bushing (134) around a vertical axis; a platform rotation motor (150) supported by the bushing (134) and configured to control the rotation of the head mounting platform (130); and a spindle motor (160) configured to control the rotation of a tool-carrying spindle (45) on the operating head (40) through a driving extension (163) arranged in a through-bore (133) obtained through the head mounting platform (130). The spindle motor (160) is fixed to and is rotationally integral with the head mounting platform (130).