A vibration proof structure of a seat apparatus for a vehicle, includes a first member and a second member movably arranged relative to each other in a first relative direction corresponding to a forward movement of a seat element in a front and rear direction of the vehicle and in a second relative direction corresponding to a rearward movement of the seat element in the front and rear direction, a first restriction wall restricting a relative movement of the first member to the second member in the first relative direction, a second restriction wall restricting the relative movement of the first member to the second member in the second relative direction, and a resistance force applying portion applying a resistance force to the first member moving in the first relative direction while not applying the resistance force to the first member moving in the second relative direction.