A contactless dual-plane positioning method is disclosed. In this method, an X ray is provided. The X ray passes through a first test piece along a light incident axis. A scattering pattern generated by the X ray passing through the first test piece, and a scatting light intensity corresponding to the scattering pattern are obtained. According to the scattering light intensity, the first test piece is pivoted along a first axis or a second axis until the scattering intensity is greater than or equal to a predetermined intensity. At least three measurement distances between a second test piece and the first test piece are then obtained. According to the measurement distances, an included angle between the second test piece and the light incident axis is adjusted by pivoting the second test piece along a third axis or a fourth axis until the differences between any two measurement distances are less than a predetermined threshold value.