Provided are a piston ring which, even when a sleeve constituted of an aluminum alloy is used, can sufficiently show the required low frictional properties, wear resistance, and low counterpart-material attacking properties, and a process for producing the piston ring. The piston ring has a rigid carbon film formed as the outermost layer thereof and serving as a sliding surface with a sleeve constituted of an aluminum alloy, wherein the rigid carbon film gives an X-ray diffraction pattern that has peaks assigned to graphite crystals. The rigid carbon film of the piston ring is formed using a chemical vapor deposition method. The rigid carbon film of the piston ring has a hydrogen content which is at least 20 atm % but lower than 30 atm %, and gives a Raman spectrum in which the ratio of the area (ID) of D-band peaks to the area (IG) of G-band peaks, ID/IG, is 0.5-2.0.