An apparatus for measuring an internal volume of a mould designed for forming hollow glass containers and divisible into two or more pieces , comprising: - a supporting element configured to support the mould pieces positioned to allow respective moulding surfaces , delimiting the internal volume of the mould, to be accessible to optical inspection means; - a laser scanning device configured to scan the profiles of a surface and obtain information on the distance between the surface and the device itself; - a slide movable relative to the supporting element along a longitudinal movement axis having a predetermined position relative to the supporting element , the scanning device being connected to the slide ; - a control unit connected to one or more actuators to produce a relative translation between the slide and the supporting element , the apparatus being characterised in that the scanning device is further movable, relative to the supporting element , by rotation about a longitudinal axis of rotation parallel to the movement axis, and in that the apparatus comprises a reference element located at a fixed position relative to the supporting element and provided with a plurality of reference points spaced in a predetermined manner and configured to generate corresponding points of discontinuity in an image of the reference element itself captured by the scanning device, wherein the reference element is curved and has a concavity facing away from the supporting element , and wherein the control unit is configured to produce a relative rotation between the scanning device and the supporting element and wherein the control unit is programmed to command a movement of the scanning device in the proximity of the reference element for scanning at least a part comprising at least one of the reference points . - a supporting element configured to support the mould pieces positioned to allow respective moulding surfaces , delimiting the internal volume of the mould, to be accessible to optical inspection means; - a laser scanning device configured to scan the profiles of a surface and obtain information on the distance between the surface and the device itself; - a slide movable relative to the supporting element along a longitudinal movement axis having a predetermined position relative to the supporting element , the scanning device being connected to the slide ; - a control unit connected to one or more actuators to produce a relative translation between the slide and the supporting element , the apparatus being characterised in that the scanning device is further movable, relative to the supporting element , by rotation about a longitudinal axis of rotation parallel to the movement axis, and in that the apparatus comprises a reference element located at a fixed position relative to the supporting element and provided with a plurality of reference points spaced in a predetermined manner and configured to generate corresponding points of discontinuity in an image of the reference element itself captured by the scanning device, wherein the reference element is curved and has a concavity facing away from the supporting element , and wherein the control unit is configured to produce a relative rotation between the scanning device and the supporting element and wherein the control unit is programmed to command a movement of the scanning device in the proximity of the reference element for scanning at least a part comprising at least one of the reference points . <EOS>