Photocatalytic hydrogen production has attracted attention as a clean solar hydrogen-generation system. High crystallinity and high surface area are important properties required for high efficiency photocatalysts. Two-dimensional semiconductor nanocrystals (nanosheets) prepared by exfoliation of layered metal oxides are ideal materials that can satisfy both of these requirements. In this study, we report a new approach to improve the photocatalytic activity of nanosheets. In general, a catalyst without co-catalyst loading has poor photocatalytic activity, while the Rh-doped oxide nanosheets exhibited high photocatalytic activity for H_2 production from a water/methanol system without co-catalyst loading. The quantum efficiency at 300 nm was 65%. The conductivity of the catalyst was decreased by doping, which indicates the RhO_6 units in the lattice of the nanosheet function as electron trap sites. The RhO_6 units in the nanosheet probably also act as reaction sites for H_2 evaluation.