This paper proposes a methodology for problem solving based on the viewpoint of Equivalent Transform Thinking (ETT) Theory, that can be expected to bring about a kind of paradigm shift. The theory was advocated as a principle of creativity by Dr. Kikuya Ichikawa in 1955, after his investigation and analysis of the past discoveries and inventions. Many of Ichikawa’s papers for the creativity were published at the Creativity Research Workshop held by Dr. Hideki Yukawa, the winner of 1949 Nobel Prize in Physics. Dr. Yukawa called the Ichikawa’s theory as “Identification Theory” in his own words, and highly praised it. In this paper, we emphasize that the viewpoint of ETT Theory is very useful not only for new technology invention but also for problem solving in the sense that appropriate equivalent viewpoint can simplify the problem to be solved. Moreover, in order to clarify that the viewpoint effectively works, we show some applications of the problem solving, taking the problem cases of combined resistance of electrical circuit and parameter estimation in compartment model, as for examples.