The authors have proposed and developed a hydrogen generation system for fuel cell vehicle, which can generate large amount of hydrogen by hydrolysis of powdery sodium tetrahydroborate (NaBH4). This system is referred to as the "STEP system" (Sodium TEtrahydroborate Power system) in this paper. However, the required amount of the hydrogen to supply to the fuel cell widely varies according to the output power of the fuel cell. Moreover, it is difficult to control the amount of the hydrogen generated by the STEP system because hydrolysis is chemical reaction. Thus, it is necessary to simulate the chemical reaction in the STEP system under various conditions in order to investigate a pressure control method. Therefore, in this research, a simulation model of hydrogen generation has been developed. In addition, in order to evaluate the simulation model, analytical data obtained from the models are compared with the experimental results.