Hyper-Kamiokande (HK) consists of a large Water Cherenkov detector, far detector (FD), and neutrino beam line, J-PARC. The FD is under construction now, and will be equipped with 20,000 PMTs whose diameter is 20 inch. It is improved and has twice better performance than that of Super-Kamiokande detector. For the 20 inch PMTs, we have been developing several types of readout electronics. They are required to utilize the improved performance as much as possible. This talk presents detailed schemes of each option and the status of R&D.