Showa Shell Oil K.K. Co., Ltd. was established on January 1, 1985. The current company was established through the merger of Showa Oil Co., Ltd. and Shell Oil Co., Ltd. The predecessor of Showa Oil Co., Ltd. was established on August 1, 1942, through the merger of three companies: Hayama Oil, Asahi Oil and Nitsu Oil. In April 1949, Showa Oil Co., Ltd. was designated as a return oil distributor for an oil distribution business. In June 1949, Showa Oil entered into a cooperation agreement linking the exchange of crude oil and imports with the Royal Dutch/Shell Group. This relationship was further strengthened with the start of equity investment in Showa Oil Co., Ltd. Royal Dutch/Shell Group in June 1951.

So it is a joint venture company that owns or is authorized to use the trademark of Anglo-Dutch Shell. Its main business is oil refining.