1. Introduction Growing interest has been paid for fabrication of micro- or nano-sized structures by using femtosecond laser induced photopolymerization or photoreduction of metal ions. Recently, the fabrication of polymer/metal composite structures using simultaneous induction of photopolymerization and photoreduction has been reported toward application in the field of flexible electronics and MEMS. In this study, we demonstrate the fabrication of polydimethylsiloxane (PDMS)/metal composite nanostructures by using femtosecond laser. PDMS is an attractive material which shows mechanical elasticity. 2. Material and method We prepared the mixture of photo curable PDMS and silver benzoate in hexane and deposited it on the cover glass. The femtosecond laser pulses which had a central wavelength of λ = 522 nm and a pulse repetition rate of 63 MHZ were irradiated to the mixture through the cover glass. The laser pulses were focused on the surface of the cover glass with an objective lens (NA 1.0). Fabricated structures were observed with optical microscope and scanning electron microscopy (SEM) after removal of the unsolidified portion. Elemental analyses of the fabricated structures were also carried out with energy dispersive X-ray spectroscopy (EDX). 3. Results and discussion Figure 1(a) shows an optical microscope image of the fabricated structure. The laser power and the scanning speed for the fabrication were 17.5 mW and 2 mm/s, respectively. Along the scanning direction, a line structure is observed. Inside the fabricated structure, translucent and turbid structures were distributed. From EDX analysis, the signal corresponding to silver was obtained on the fabricated structure. These results indicate that the line structure was composed of PDMS and silver. Fig. l(b) is the SEM image of the fabricated structure. The line width of the fabricated structure was less than 500 nm. This method has the potential to fabricate elastic nanostructures with plasmonic optical properties as well as conductivity for applications such as flexible sensors.