The present disclosure provides a seat position adjustment apparatus with improved assemblability, wherein the assemblability is improved and the weight is reduced by individually modifying the shapes of a mounting part and a gear part and improving their coupling structure, the seat position adjustment apparatus including a driving unit including a motor in which a drive shaft is formed, a gear part, wherein a curved surface part extending along a direction of rotation about a first axis extending bilaterally is formed in an outer portion of the gear part, and the gear part is gear-coupled to the drive shaft, a rod part coupled to the gear part such that the rod part passes through the gear part, receives power from the drive shaft, and moves forward or rearward, and a mounting part, wherein upper portions of a curved plate structure surrounding the curved surface part at a front and a rear of the gear part, respectively, envelop the rod part to form respective through-holes each having a vertical length that is relatively greater than a vertical thickness of the rod part, wherein, in a state in which the mounting part is fixed, a seat connected to the rod part is moved in accordance with a movement of the rod part.

An occupant knee support device provided in a vehicle includes a knee outer side surface support member and a knee lower surface support member. The knee outer side surface support member is disposed in a side part of the seat surface part in a stored state, protrudes forward and upward beyond the seat surface part in a support state to support an outer side surface of a knee of the occupant. The knee lower surface support member is, in the stored state, provided in a vicinity of a front end part of the seat surface part and separated from a lower surface of the knee of the occupant. The knee lower surface support member is configured to support the lower surface of the knee of the occupant in the supported state.