In this study, artificial cemented sand made of a few portland cement and Nak-Dong river sand was researched closely to investigate cementing effect quantitatively through unconfined tests and triaxial tests. The peak strength and elastic modulus increased and dilation of cemented sand was restricted by the cementation, but after breakage of the cementation, dilation and negative excess pore water pressure increased. In stress-strain curve, strain-softening behavior appeared in drained condition but strain-hardening behavior was appeared in undrained condition as a result of the increase of effective stress. The test was quantitatively analyzed by multiple regression models, correlating each response variable with input variable. The equations are valid only over the range investigated. Its adjusted coefficient of determination was $0.81{sim}0.91$, and dry density is important factor for estimating strength of cemented sand.