To provide a photocatalyst dispersion liquid that is stably dispersed and has high antibacterial action, a photocatalyst composite material that has high activity and prevents film from peeling, and a photocatalyst device.MEANS FOR SOLVING THE PROBLEM: A photocatalyst dispersion liquid contains a main catalyst particle, and an alumina hydrate particle to which a silicon compound having a chemically bonding reactive group is bound.SELECTED DRAWING: Figure 1【課題】分散が安定で抗菌作用が高い光触媒分散液、高活性で膜が剥がれにくい光触媒複合材料、および光触媒装置の提供。【課題手段】主触媒粒子と、化学結合性反応基を有するケイ素化合物が結合しているアルミナ水和物粒子と、を含有する光触媒分散液。【選択図】図1