A seat cushion adjusting apparatus includes a support member configuring a frame of a seat cushion, a seating member supported by the support member and configuring an outer shape of the seat cushion, an adjustment member fastening a front end portion of the seating member in a longitudinal direction of a seat, and a movement mechanism rotatably connecting the adjustment member and moving the adjustment member relative to the support member in the longitudinal direction, the movement mechanism including a transmission member extending in a width direction of the seat at a front side of the support member, a lever rotatably connected to the support member, a first gear plate rotatably connected to the lever and the transmission member and having a first gear, and a second gear plate rotatably connected to the transmission member and the adjustment member and having a second gear meshing with the first gear.