A road surface friction coefficient estimating device includes a braking/driving force detecting section for detecting the braking/driving force of a wheel during traveling, a slip ratio detecting section for detecting the slip ratio of the wheel during traveling, and a road surface μ calculating section for estimating the relationship between the detected braking/driving force and the detected slip ratio on the basis of the ratio between the detected braking/driving force and the detected slip ratio, the correlation between the braking/driving force and the slip ratio in the case of the reference road surface, and at least either the detected braking/driving force or the detected slip ratio.