Super-Kamiokande(SK) is a large water Cerenkov detector which consists of 50 kton pure water as a target of observation of atmospheric, solar, supernovae and accelerator neutrino and as a source of nucleon decay. Cherenkov lights emitted by charged particles from neutrino interaction at 22.5 kton of fiducial volume are viewed by 11,146 inward-facing 20-inch photomultiplier tubes(PMTs) during the first run of the detector, SK-I. The two subsequent run periods, SK-II and SK-III had 5,182 and 11,129 PMTs respectively. The outer detector surrounding the inner volume has been instrumented with 1,885 outward-facing 8-inch PMTs and used primarily as a veto. Although Super-Kamiokande has provided enormous amount of data and physics results [1] for more than 10 years since the observation started in 1996, DAQ electronics and computers are upgraded, then, SK started its physics data taking as SK-IV in October 2008. Atmospheric and solar neutrino oscillation analysis results, nucleon decay search results and search for neutrinos from supernovae in SK-I+II+III (before electronics upgrade) data and preliminary results on neutrino observation in SK-IV are reported in the following sections.