Surface modification was performed oil high-pressure densified silica glass by CO laser irradiation. Microbumps were formed oil the silica glass Surface due to the relaxation of the compacted structure by the irradiation. The relaxed area reached a depth of about 40 mu m, and the Volume expansion estimated from the relaxed area was consistent with the volume expansion at the surface. The microbumps were arrayed at a minimum interval of 15 mu m, which acted as a microlens array. Moreover, microbumps were formed successfully on both sides of the thin glass plate by irradiation from one side.