Two-photon lithography allows us to fabricate arbitrary three-dimensional structures with micro/nano-spatial resolution. The intrinsic three-dimensional spatial resolution of two-photon lithography is a promising tool for developing a variety of novel photonic and mechanical nano-devices. In addition, two-photon lithography makes it possible to study the properties of polymers of micro/nano-meter dimension [1-4]. In this presentation, we show the evidence that the elasticity and the transition temperature of polymers start to show size-dependent characteristics when the size of the polymer decreases down to a few hundreds of nanometers. We fabricated free-standing polymer nano-wires in the shape of coil spring by two-photon lithography, and measured the elasticity of the nano-wires by applying a mechanical tension onto the springs through laser trapping technique under temperature control. From the stretching length of the spring generated by a certain optical force, the spring constant of the spring and the shear modulus of polymer were calculated from simple Hook’s law. The material we used is a compound of methyl-methacrylate, dipentaerythritol hexaacrylate, benzil, and 2-benzyl-2-(dimethylamino)-4’-morpholino-butyrophenone. We scanned a light spot of a Ti:Sapphire laser at 780 nm with a pulse width of 80 fs focused by a 1.4 NA microscope objective to shape the polymer nano-wires suspended by a thick pillar. We observed that the elasticity of the polymer, which is usually an invariable coefficient, changes according to the thickness of the polymer wire. Furthermore, we changed the temperature of the entire polymer structures from -20 to 40 °C with measuring the elasticity of the springs. We observed phase transition of polymer wires with a rapid change of the share modulus, which also shows a size-dependent behavior. Recently, the similar experimental results, i.e. the drop of the glass transition temperature, were also reported in thin polymer nano-films. Our result is a clear evidence of such a nano size-effect of mechanical properties in polymers confirmed from free-standing polymer nanostructures. S. Nakanishi, H. Yoshikawa, S. Shoji, Z. Sekkat, and S. Kawata, J. Phys. Chem. B 112, 3586-3589 (2008).  S. Nakanishi, S. Shoji, S. Kawata, and H.-B. Sun, Appl. Phys. Lett. 91, 063112 (2007). H. Ishitobi, S. Shoji, T. Hiramatsu, H.-B. Sun, Z. Sekkat, and S. Kawata, Opt. Express 16, 14106-14114 (2008). S. Kawata, H.-B. Sun, T. Tanaka, and K. Takada, Nature, 412, 697 (2001).