This paper reports facile integration of a free-standing nanofiber membrane in a microfluidic device by electrolyte-assisted electrospinning, called ELES. We introduced an electrolyte solution as a collector for nanofibers, which enables flexible shaping of the collector from a two-dimensional to three-dimensional geometry. Furthermore, the electrolyte solution, filled in a microchannel of a microfluidic device, allows the nanofiber membrane to be spontaneously integrated with the device.