Thirty years have passed since supernova neutrinos from SN1987A were observed by Kamiokande, IMB and Baksan detectors. Although many detectors in the world have been monitoring supernova neutrinos, no other supernova burst neutrinos has been observed yet. First, I will review what we have learned from the observation of SN1987A. Then, I will discuss what we can learn from the next galactic (+LMC) supernova burst if it is detected by Super-Kamiokande (SK). The project to load gadolinium to the SK tank in order to tag neutrons, called the SK-Gd project, is being prepared. Its main physics motivation is an observation of supernova relic neutrinos (SRN). I will review what the SRN observation tell us in astrophysics. In addition, other impacts from SK-Gd will be discussed.