Abstract: The invention concerns a three-dimensional measuring device, which comprises: a base (5) intended to be fixed to a support assembly (6) and lying in a first plane, a plate (14) mounted so as to rotate on the base (5) about a first axis (Z), said plate being equipped with a first sensor (c1) determining the angle of rotation (?) of the plate about this first axis (Z), a single rocking telescopic arm (2), a first end of which is articulated on the plate (14) about a second axis (X) orthogonal to the first axis (Z), the angle of rotation (?) of said arm about the second axis (X) being determined by a second sensor (c2), the second end of the single telescopic arm being provided with a measuring feeler (3), and the said single arm being equipped with a third sensor (c3) determining the elongation length (?) of the arm in translation, so that the spatial position of the measuring feeler is determined by its polar coordinates (?, ?, ?) in the fixed three-dimensional reference frame consisting of the base (5) once t