Provided is a seat sliding device. The seat sliding device comprises a fixed-side rail, a movable-side rail, a lock portion, an elastically deforming portion, and a releasing member. The lock portion is displaceable between a restraint position and a release position. The elastically deforming portion comprises: a linear portion that is an elastically deformable portion extending in a direction approximately parallel to a longitudinal direction of the movable-side rail; and an engaging portion protruding from an extending-direction leading end portion of the linear portion in a direction approximately perpendicular to an extending direction of the linear portion. The releasing member comprises: a first engaged surface that is contactable with the engaging portion from one end side in the extending direction; and a second engaged surface that is contactable with the engaging portion from the other end side in the extending-direction.