An electric connector of the snap-in-fitting system comprises a couple of male and female connector members both made of an electrically-conductive material. The female connector member has a female engaging part or outer ring part for snap-in-fitting and the male connector member has a male engaging part or outer ring part to be fitted in and engaged with the female engaging part by snap-in-fitting. The interaction part in snap-in-fitting of the male engaging part and the female engaging part is an inclined engaging surface and adapted to apply load to the female engaging part so as to always urge the female engaging part outward. Preferably, the inclined engaging surface is a tapered surface convergent toward the male connector member side. Such an electric connector of the snap-in-fitting system is useful for the connection of a storage power supply unit of an electric vehicle and of a battery unit of a portable type electronic device, particularly an ultra capacitor or a storage cell (capacitor cell) of a battery.