Photocatalytic and photoelectrochemical approaches to solar hydrogen production in our group were introduced. In photocatalytic water splitting system using NiO x / TiO 2 powder photocatalyst with concentrated Na 2 CO 3 aqueous solution, solar energy conversion efficiency to H 2 and O 2 production (STH efficiency) was 0.016%. In addition, STH efficiency of visible light responding photocatalyst, NiO x / promoted In 0.9 Ni 0.1 TaO 4 , was estimated at 0.03%. In photoelectrochemical system using an oxide semiconductor film phptoelectrode, STH efficiencies of meosporous TiO 2 (Anatase) , mesoporous visible light responding S-doped TiO 2 (Anatase) and WO 3 film were 0.32-0.44% at applied potential of 0.35 V vs NHE, 0.14% at 0.55 V and 0.44% at 0.9 V, respectively. Finally, solar hydrogen production by tandem cell system composed of an oxide semiconductor photoelectrode, a Pt wire counter electrode and a dye-sensitized solar cell (DSC) was investigated. As photoelectrodes, meosporous TiO 2 (Anatase), mesoporous S-doped TiO 2 (Anatase), WO 3 , BiVO 4 and Fe 2 O 3 film were tested. STH efficiency of tandem cell system composed of a WO 3 film photoelectrode, and a two-seriesconnected DSC (Voc = 1.4 V) was 2.5-2.8%. In conclusion, it is speculated that more than 5% STH efficiency will be obtained by tandem cell system composed of an oxide semiconductor photoelectrode and a two-series-connected DSC in near future. This suggests a cost-effective and practical application of this system for solar hydrogen production.