The present invention provides a three-dimensional nanofibrous scaffold for tissue regeneration, which is increased in porosity and thickness to enlarge the surface area thereof, thereby enabling cell adhesion at a high density, and a method for fabricating the same. The method for fabricating a three-dimensional nanofibrous scaffold for tissue regeneration includes the steps of: (a) preparing a polymer solution; (b) preparing a nanofiber matrix, in which a plurality of nanofibers is entangled with each other, from the polymer solution prepared in step (a) using electrospinning; and (c) immersing the prepared nanofiber matrix in a solution and subjecting the solution to ultrasonication, thereby increasing the thickness and porosity of the nanofiber matrix. According to the inventive scaffold fabricating method, the nanofiber matrix prepared by using electrospinning is ultrasonicated in a solution, so that a three-dimensional nanofibrous scaffold with improved thickness and porosity can be provided in a simple and low-cost manner.