An experimental storage system for agricultural products to control temperature and gas composition was constructed. The experiment in which tomato storage characteristics at 25°C under normal atmospheric condition could be obtained with high precision was made by using this apparatus. The immature tomatoes, which typically showed the post-ripening behavior, were used as the experimental samples. For the storage characteristics, O₂ and CO₂ concentrations, total pressure, temperature, and relative humidity were continuously measured while the ethylene and alcohol concentration were determined by inner gas sampling. Surface color and the sugar component changes were obtained as the individual characteristics of tomato. As a result, the O₂ and CO₂ respiration rates reduced largely, and the ethylene evolution highly increased with post-ripening. The surface color also dynamically changed. Moreover, glucose, fructose, sucrose contents in tomato measured by FT-IR/ATR (Attenuated Total Reflection) method before and after storage did not change with post-ripening.