A road surface friction coefficient estimating device includes a means which finds a first estimated value Mnsp_estm of an external force to be compared (S102 to S116, S118-2), a means which finds a second estimated value Mnsp_sens (S118-1), and a plurality of increasing/decreasing manipulated variable determining means 34_k, each of which determines the increasing/decreasing manipulated variable Δμ_k of the friction coefficient estimated value on the basis of the first estimated value Mnsp_estm and the second estimated value Mnsp_sens, and updates the friction coefficient estimated value according to Δμ_k. The increasing/decreasing manipulated variable determining means 34—1 and 34—2 determine Δμ—1 and Δμ—2 according to a deviation in filtering value between the first estimated value and the second estimated value, and the increasing/decreasing manipulated variable determining means 34—3 determines Δμ—1 according to the deviation between the first estimated value and the second estimated value.