Hydrogen energy is one the new energy and applied to fuel-cell powered vehicle already. But nowadays, almost hydrogen is produced from steam reforming method and much CO2 is emitted. In the future, no-greenhouse gas emission method is needed. We focus on biomass conversion by using cyanobacteria. In this research we select thermophilic cyanobacteria Synechococcus sp. strain H-1 because it has high specific growth rate and contamination of other bacteria cannot occur under high temperature condition. We investigated hydrogen production mechanism and sustainable hydrogen production.