Energy is essential for goods and services. Japan's economy is dependent on imported energy which is 85% per year, the highest percentage among industrialised nations. The study measures energy supply security (ESS). Four indices; dependency index, intensity index, local production index and composite index are constructed and statistical models are formed out to investigate the significance and the sensitivities between the ESS indexes and the input parameters that are; petroleum prices (PP), gross domestic products (GDP), total primary energy supply (TPES), energy consumption (PCEC), renewable energy (REN), CO2 emissions (CEM), population (P), traffic volume (TV), human development index (HDI) and mean of democracy indexes of energy suppliers (DI). A comprehensive methodology is used with five statistical procedures including simple correlation analysis, multiple linear regression models, stepwise multiple linear regression model, principal component analysis and cluster analysis. Empirical results indicate that PCEC, P and HDI have significant effect on ESS.