The mechanical properties of polydimethylsiloxane networks with a supercoiled structure, which are prepared by removing solvent from the networks crosslinked at low concentration, have been investigated. The fractal dimension D of the supercoiled structure has been estimated to be D = 2.5 from the dependence of stress on the elongation ratio lambda on the basis of the concept of the Pincus blob. The obtained D is larger than for Gaussian chains (D = 2), and smaller than for ’polymer chain in an array of obstacles’ (PCAO) models (D = 3 or 4). The deswollen network prepared at ca 9% has exhibited a remarkable high extensibility reaching lambda congruent to 18, as a result of the reduction of the distance between network junctions on deswelling and the decrease of trapped entanglements due to the low concentration at crosslinking. From comparison of the stress-elongation relationships in the deswollen and preparation state, the deswollen networks with a supercoiled structure after a large elongation are expected to have the same topological structure for the network chains as the original networks under elongation.