The surface structures of Ni introduced by polishing with diamond paste, electric discharge machining, cutting tool machining and laser beam machining were observed with a transmission electron microscope. Observations were made from directions both vertical and parallel to machined surfaces. Surface structure can be classified into three component substructures. The first one, within a depth smaller than several μm, is specific for each of machining processes. This provides information for the phenomenon which took place in the front of the machined material. The second one in the depth up to around 200μm is cellular structure of dislocations. Cells increase their size gradually with depth and finally turn to dislocation trangles. Sizes and shapes of cells, and their orientation misfit show the history of stress condition. The surface quality by each machining was compared by evaluating the stress induced during machining processes. The last one in the depth larger than 200μm which is composed of tangled dislocations shows an extension of affected zone of machining.