SEAT SLIDING DEVICE AND ASSEMBLING METHOD OF LOCK SPRING USED IN SEAT SLIDING DEVICE

A seat sliding device includes: a lower rail; an upper rail; a lock member; a spring member; and an operation lever, the first fixing portion of the spring member which has a ring shape having an outside diameter greater than a width between the pair of the side walls of the upper rail, which has a spring force in a diameter increasing direction between the pair of the side walls of the upper rail, and which includes a first mounting portion and a second mounting portion that are configured to be mounted and fixed, respectively, in the first hole portion and the second hole portion by the spring force.