A single phase of Ba₃Ta₆Si₄O₂₆ consisting of one-dimensional TaO₆ chains has been synthesized by an amorphous metal complex (AMC) method employing water soluble materials, tantalum peroxolactate and silicon tetrapropyleneglycoxide. In contrast, a polymerizable complex method of another solution process gave a mixed phase of Ba₃Ta₆Si₄O₂₆ and orthorhombic BaTa₂O₆. It has been suggested that homogeneity of the precursors strongly affected the phase purity. Ba₃Ta₆Si₄O₂₆ produced hydrogen and oxygen from water under ultraviolet irradiation. Thus, the present research revealed that Ba₃Ta₆Si₄O₂₆ is an active photocatalyst for water splitting. Ba₃Ta₆Si₄O₂₆ prepared by the AMC method showed higher activity than that prepared by a solid state reaction.