Here, we developed a device integrated with a nanochannel and nanostructures to slow DNA translocation velocity. We found that translocation velocity of a single DNA molecule inside a nanochannel was decreased by pre-elongating it using some nanostructures, such as a shallow channel or nanopillars. This decrease of the translocation velocity was associated with the DNA mobility change, which is an intrinsic parameter of DNA molecules and unaffected by an electric field.