High efficiency drying is one of the challenges to utilize wet biomass as solid fuel. In addition, usually wet biomass has stinky smell and includes hazardous bacteria, so to collect and convey wet biomass is difficult. We propose a novel pretreatment technology for wet biomass. It is the hydrothermal reforming employing saturated steam at 473K with mixing rice husk. This pretreatment technology has two features; one is increasing effect of apparent drying rate of solid products, another is reforming effect of stinky and distinct odor of sewage sludge. As results of experiments used sewage sludge as model wet biomass, the apparent drying rate of the solid product became four times as large as that of the reactant. And, concerning the stinky smell, the concentrations of H_2S and NH_3 originated from the solid product decreased compared with the sewage sludge by this reforming. This hydrothermal reforming needs little energy compared with conventional indirect heating drying. So, this hydrothermal treatment is appropriate as pretreatment for wet biomass fuelization.