We present a simple and an inexpensive method for the fabrication of a nano-fluidic filter and a nano-pore micromixer using self-assembly of nano-spheres and surface tension. Colloid-plug was formed by surface tension of liquid in a microchannel to fabricate nanofluidic filter. When colloid is evaporated, nano-spheres in a colloid are orderly stacked by a capillary force. Orderly stacked nano-spheres form 3-D nano-mesh which can be used as a mesh structure of a fluidic filter. We used silica nano-sphere whose diameter is $567{pm}85nm$, and silicon micro-channel of $50{mu}m$-diameter. Fabricated nano-fluidic filter in a micro-channel has median pore diameter of 158nm which was in agreement with expected diameter of the nano-pore of $128{pm}19nm$. A nano-pore micromixer consists of $200;{mu}m-wide,;100;{mu}m-deep$ micro-channel and self-assembled nano-spheres. In the nano-pore micromixer, two different fluids had no sooner met together than two fluids begin to mix at wide region. From the experimental study, we completely apply self-assembly of nano-spheres to nano-fluidic devices.