A support apparatus for supporting at least one neck mold of a plastic container, the apparatus being adapted to be fastened to a lower surface of a rotating device of an injection blow molding machine of plastic containers, said support apparatus comprising - a pair of plates defining a longitudinal axis, said plates being adjacent to each other along the longitudinal axis and separable from each other transversely to said longitudinal axis, and being kept adjacent in a normally closed state by elastic means; wherein each plate is provided with at least one respective recess positioned so that, when the plates of said pair of plates are in the normally closed state, at least two recesses are adjacent to each other along said longitudinal axis so as to define a seat for a neck mold comprising a pair of split molds, each split mold being capable of being accommodated in a recess of a respective plate; - a pair of side guides transverse to said longitudinal axis, adapted to be fastened to said lower surface of the rotating device, each side guide being adapted to support a respective end of the pair of plates from the bottom; characterized in that the side guides are provided with a respective locking system for locking or unlocking the pair of plates to/from said pair of side guides so that, in an unlocking position, the pair of plates can be extracted transversely to the longitudinal axis thereof by sliding on the side guides. said support apparatus comprising - a pair of plates defining a longitudinal axis, said plates being adjacent to each other along the longitudinal axis and separable from each other transversely to said longitudinal axis, and being kept adjacent in a normally closed state by elastic means; wherein each plate is provided with at least one respective recess positioned so that, when the plates of said pair of plates are in the normally closed state, at least two recesses are adjacent to each other along said longitudinal axis so as to define a seat for a neck mold comprising a pair of split molds, each split mold being capable of being accommodated in a recess of a respective plate; - a pair of side guides transverse to said longitudinal axis, adapted to be fastened to said lower surface of the rotating device, each side guide being adapted to support a respective end of the pair of plates from the bottom; - a pair of plates defining a longitudinal axis, said plates being adjacent to each other along the longitudinal axis and separable from each other transversely to said longitudinal axis, and being kept adjacent in a normally closed state by elastic means; wherein each plate is provided with at least one respective recess positioned so that, when the plates of said pair of plates are in the normally closed state, at least two recesses are adjacent to each other along said longitudinal axis so as to define a seat for a neck mold comprising a pair of split molds, each split mold being capable of being accommodated in a recess of a respective plate; - a pair of side guides transverse to said longitudinal axis, adapted to be fastened to said lower surface of the rotating device, each side guide being adapted to support a respective end of the pair of plates from the bottom; characterized in that the side guides are provided with a respective locking system for locking or unlocking the pair of plates to/from said pair of side guides so that, in an unlocking position, the pair of plates can be extracted transversely to the longitudinal axis thereof by sliding on the side guides.