In this paper, we consider the obstacle problem for the inhomogeneous p-Laplace equation div(vertical bar del(u)vertical bar(P-2)del u) = f.chi{u>0}, 1 < p < 2, where f is a positive, Lipschitz function. We prove that the free boundary has finite (N - 1)-Hausdorff measure and stability property, which completes previous works by Caffarelli (J. Fourier Anal. Appl. 4(4-5) (1998) 383-402) for p = 2, and Lee and Shahgholian (J. Differ Equ. 195 (2003) 14-24) for 2 < p < infinity.