Mechanical deformation can lead to various surface changes such as surface electronic behavior. The effect of deformation on work function (WF) has been studied extensively, but the mechanism responsible for such effect has been unclear. In this study, we measured the variations in the WF typically of an Al–Mn alloy with respect to deformation under dynamic tensile conditions using a scanning Kelvin probe. Furthermore, we also investigate the contribution of surface morphology, represented by roughness, caused by different deformation conditions to the WF. It was demonstrated that the WF depends strongly on both deformation and deformation speed, whereas roughness depends on deformation but hardly deformation speed. The present study therefore suggests a significant role of dislocation mechanism in determining the WF although surface morphology or roughness associated with deformation also affects the WF.