This study explores the effect of normal stress levels and asperity scales on roughness mobilization characteristics through joint shear tests, and suggests a new method for quantifying rock joint roughness. Two-dimensional joint surface profiles were scanned by using a digital camera-based 3D scanner system, and were classified into a small scale of roughness (unevenness) and a large scale of undulation (waviness). Joint surface profile specimens, duplicated using a wire-cut electric discharge machining method, were tested for shear behaviors. For waviness showing non-stationary signals, the mobilized roughness is not constant but varies nonlinearly at normal stress levels. However, for unevenness showing noise and a stationary signal, the ultimate shear strength appears at a low normal stress level.