A method of detecting the shape of flat products, which comprises applying, through an exciter, to an examined objects in its width, exciting signal generated in an exciting signal generator, as an exciting force, concurrently detecting the deflection of said examined object taking place due to the application of such exciting force at a plurality of points on said examined object in the width direction, correlating the exciting signal and the so detected values of deflection in the signal processing circuit, and determining the tension of said examined object at respective points on said examined object. The tension distribution on said examined object, in the width direction can therefore by determined, whereby the shape of said examined object can be ascertained.