Eco-driving support systems (EDSSs) are divided into two types; a direct EDSS and an indirect EDSS. The former intervenes drivers' operation directly to improve fuel economy automatically and deprives drivers of an oppotunity to try to perform eco-driving. Therefore, they could not master the eco-driving technique. The indirect EDSS provides only information about results of the driving behavior to encourage spontaneous effort to improve fuel economy. The present study performed driving simulator experiments to verify the differences of influence of the two EDSSs on proficiency of the eco-driving. We discuss the results from a viewpoint of FUBEN-EKI (FUrther BENEfit of a Kind of Inconvenience), proposed as a novel system design methodology, and then clarify the relationship between the degree of actively device and the proficiency of eco-driving skill.