This paper introduces the methods of hydrogen peroxide storage test and storability of concentrated hydrogen peroxide is estimated. Using the method of simple concentration measuring, storability was evaluated. Experiment variables were the amount of stabilizer in hydrogen peroxide, storage temperature, and caps of vessels. The experiments were performed during 8 months to 24 months. High purity hydrogen peroxide had much better storability than hydrogen peroxide with much stabilizer. In addition, the case using paraffin film which did not react with hydrogen peroxide for covering showed better storability. The temperature is very important variable in hydrogen peroxide storage. So, when hydrogen peroxide was under $10^{circ}C$ storability of hydrogen peroxide is much improved.