We demonstrated the use of laser-induced reshaping to produce periodic silicon nanostructures (PSNs) with different geometries. Periodically located silicon nanostructures were preformed by dry etching of a silicon wafer covered with a monolayer of self-assembled polystyrene nanospheres. These PSNs were reshaped under ambient conditions by irradiation with two kinds of nanosecond lasers (532 nm and 355 nm). The effects of the irradiation parameters on the reshaped geometry were systematically investigated. Vertical growth of the irradiated PSNs resulted from the epitaxial deposition of rich silicon vapor during laser irradiation. However, the growth was limited even with higher laser fluence because of the nanoscale structure, the size of which is smaller than the melting depth induced by the nanosecond lasers. The reshaped PSNs displayed reflection spectra that are tunable by varying the characteristics of reshaping-laser input. This method offers a promising approach for the site-selective fabrication of optically tunable 3D nanostructures.