Abstract: “Energy cognition” is a precondition for the formulation and implementation of energy policies, while energy policies are the product of “energy cognition”. In post-war Japan, cognition of energy security has undergone a structural transformation from a “single view” to a “comprehensive view”. In terms of connotation, it has undergone a process of “coal security concept” -“oil security concept” -“3E security concept” - “3E+S security concept”. Both the “coal security concept” and the “oil security concept” are based on a single energy source, which featured the “incrementorientedness” in policy design and practice. In the early 1990s, Japan deepened its cognition by adding “economic efficiency” and “environmental” to the single “energy security”. However, the 311 earthquake and the Fukushima nuclear accident revealed the shortcomings of the “3E security concept” . In response, Japan added “safety“ and upgraded it to the “3E+S security concept”, which balanced security with stability, efficiency and environmental protection. After the Russia-Ukraine conflict, there are emerging changes of the cognition of energy security in Japan,such as from a defensive approach to energy risks to active participation in global energy security governance, and a combination of the goals in “ex-Russia” and “ex-carbon”.

Key words: Japan, oil, Russia-Ukraine conflict, energy, security concept