Purpose of epidermal ridges of humans have been said to avoid slippage and to increase sensitivity of tactile perception. In the present study, meaning of detailed geometry of each epidermal ridge is investigated. First, cross-sectional geometry of epidermal ridges are measured using imprint material. It is found that the geometry of epidermal ridges are between that of arc and trapezoid. Then, finite element contact analyses between finger section model and a flat plate are conducted. It is found that normal contact forse distribution of human epidermal ridge is much uniform compared with those for arc and trapezoid. It is also found that rapid entire slippage of an epidermal ridge occurs when tangential traction is applied. Finally, eigen value analysis is conducted. It is found that eigen frequency of the epidermal ridges agrees with FA I mechanoreceptor's sensitive frequency.