THz measurement device (7, 28) for measuring at least one wall thickness (d) of a wall region (5, 6), which has an inner face and an outer face, of a tubular measurement object, wherein the THz measurement device (7, 28) has: a main THz sensor (8, 30-8) for transmitting a main THz beam along a first optical axis through an axis of symmetry of the measurement object and for receiving THz radiation which is reflected on the outer face and the inner face along the first optical axis, an additional THz sensor (9, 18, 19, 30-i) for transmitting an additional THz beam along a second optical axis which is displaced with respect to the first optical axis through a sensor angle (α, β) and which at least temporarily during the measurement method does not extend through the axis of symmetry, and for detecting the additional THz beam which is reflected back along the second optical axis, an evaluation and control device which is configured to receive a first signal amplitude of the main THz sensor (8, 30-8) and a second signal amplitude of the additional THz sensor (9, 18, 19, 30-i) and to establish reflection peaks in the signal amplitudes (S1, S2), characterised in that the evaluation and control device is further configured to detect an inner wall thickness deformation when - it establishes in the first signal amplitude an external reflection peak of the outer face of the wall region (5, 6) without the internal reflection peak of the inner face of the wall region (5, 6) and - it establishes in the second signal amplitude an internal reflection peak of the inner face of the wall region (5, 6). a main THz sensor (8, 30-8) for transmitting a main THz beam along a first optical axis through an axis of symmetry of the measurement object and for receiving THz radiation which is reflected on the outer face and the inner face along the first optical axis, an additional THz sensor (9, 18, 19, 30-i) for transmitting an additional THz beam along a second optical axis which is displaced with respect to the first optical axis through a sensor angle (α, β) and which at least temporarily during the measurement method does not extend through the axis of symmetry, and for detecting the additional THz beam which is reflected back along the second optical axis, an evaluation and control device which is configured to receive a first signal amplitude of the main THz sensor (8, 30-8) and a second signal amplitude of the additional THz sensor (9, 18, 19, 30-i) and to establish reflection peaks in the signal amplitudes (S1, S2), characterised in that the evaluation and control device is further configured to detect an inner wall thickness deformation when - it establishes in the first signal amplitude an external reflection peak of the outer face of the wall region (5, 6) without the internal reflection peak of the inner face of the wall region (5, 6) and - it establishes in the second signal amplitude an internal reflection peak of the inner face of the wall region (5, 6). - it establishes in the first signal amplitude an external reflection peak of the outer face of the wall region (5, 6) without the internal reflection peak of the inner face of the wall region (5, 6) and - it establishes in the second signal amplitude an internal reflection peak of the inner face of the wall region (5, 6).