Three-dimensional (3D) micromachining of photosensitive glass is demonstrated by photochemical reaction using femtosecond (fs) laser for lab-on-a-chip application. True 3D hollow microstructures embedded in the glass are fabricated by fs laser direct writing followed by heat treatment and successive wet etching. The modification mechanism of the photosensitive glass by the fs laser and advantage of this process are discussed. Various microcomponents for the lab-on-a-chip devices such as microfluidics, microvalves, microoptics, microlasers, etc. are fabricated by using this technique and their performance is examined .