Predicting how the electric vehicle market will develop in the future is an important issue, not only for countries that have been leading the car market, such as Japan, but also for developing countries. Thus, in order to predict the diffusion of electric vehicles, the diffusion speed and price transition of existing cars were analyzed quantitatively, and research was performed to clarify the optimum prediction method for the diffusion rate of a car. In a prior study, the diffusion speed and price transition of new products after the commencement of sales were studied using consumer electronics products. The key roles played by the engineering development and the production and sales of a key device for each consumer electronics product were established. Furthermore, the obtained results could be extended to the auto industry, where the same tendency is observed. In this study, the results were expressed by a quantitative pattern and applied to the prediction of the diffusion speed and price transition of an electric vehicle. First, in relation to the diffusion, it was found that the countrywide establishment of quick charge stations has priority over a reduction in the price of an electric vehicle. Next, in order to predict the diffusion speed, electric vehicles were divided into compact EVs (replacements for compact cars) and micro-EVs (think of a product category between a compact car and a motorcycle), and were analyzed individually. Each key device was specified, and estimations were made of its development, production, and supply. The use of this method revealed that the diffusion rate for compact EVs will reach 20% approximately 14 years from the commencement of sales and that the diffusion speed for micro-EVs is dependent on the battery development speed.