Human genome project has now been completed. At the next stage, the analysis of the DNA diversity originated from each individual is a very important aspect. It requires a method that can determine the base-pair sequence quickly and easily for fast and effective analysis. Separating the biochemical samples by electrophoresis is one of the analysis processes. Recently, electrophoresis has been performed in the fine channel formed on various substrates. By utilizing a microchannel chip for electrophoresis, the dead volume of the reagent and detection apparatus, and energy are reduced. To improve the separation performance of microchannel chip, the width of the channel should be narrower. On the other hand, the volume of the sample that can be introduced is restricted. Then, the channel is filled with ionic solution, and the top of the substrate is covered with a plate for shallow channel, so as not to cause current leakage induced by applying high voltage during electrophoresis. But, it requires a high quality substrate-cover adhesion. technique. We propose a high-aspect-ratio open-top microchannel plate. The high-aspect-ratio structure increases the sample and reagent volume inside the channel without increasing the channel width, which results in an enhancement of the detection sensitivity. And the buffer solution is introduced only before the measurement and sequential supply from an external source is not needed. The chip is standalone. The deep channel leads to another advantage. Its deep depth prevents overflow of the solution to the uncovered channel. By avoiding the difficult sealing process, the fabrication process become easy and high-throughput is realized.