A tire shape measuring system measures a surface shape on the basis of an image of a line of light (a light section line) emitted to a surface of a relatively rotating tire using a light-section method. The shape measuring system includes a light projector for emitting a plurality of lines of light onto a tire surface in directions different from a direction in which the height of the surface is detected so as to form a plurality of separate light section lines and a camera for capturing images of the light section lines in directions in which chief rays of the lines of light are specularly reflected by the tire surface. The shape measuring system individually detects the coordinates of the light section lines from images of pre-defined independent image processing target areas for each captured image and calculates the distribution of the surface height using the detected coordinates.