Means for measuring a working machine's structural deviation from five reference axes includes a main sensing body bonded with a main axis of the working machine (or controlled to revolve), and a lighting unit set around the main sensing body to circle about the main sensing body with a fixed radius (or the lighting unit radiates a light on the main sensing body from that radial distance and circles along with the main sensing body) such that as soon as the main sensing body has detected an optical signal, it is converted to an error signal informing of the working machine's structural deviation in two or three dimensional displacement.