A seat slider device may include: a lower rail attachable to a body of a vehicle and including grooves arranged in a for direction of the lower rail; an upper rail attachable to a seat and slidably engaging with the lower rail; and a lock lever including a plurality of protrusions configured to engage with the grooves, supported by the upper rail to be swingable in a direction bringing the protrusions close to the grooves and in a direction bringing the protrusions away from the grooves, and biased in the direction bringing the protrusions close to the grooves. A portion of the lock lever between a pivot of the lock lever and the protrusions may have elasticity such that the portion flexes in the direction bringing the protrusions close to the grooves and in the direction bringing the protrusions away from the grooves.