To provide a surface treatment method capable of holding lubricating oil or a lubricant to the face to be worked for a long time.

According to this invention, since depressed parts 30 capable of storing lubricating oil 61 are formed on the sliding face in a work 10 as the face to be worked by the shock wave of laser peening, the lubricating oil 61 can be held to the sliding face for a long time. Further, the crystals in the sliding face of the work 10 are fractionated by the shock wave of the laser peening, also, the propagation of cracks is suppressed, and its stress corrosion cracking resistance is improved. Further, it is also possible that the powder or film of a metal or the like is driven into the surface part of each depressed part 30, so as to harden the surface layer, thus its wear resistance and sliding resistance can be improved.