A seat height adjustment apparatus includes a stepped portion provided on a bottom plate of a seat and formed in a stepped configuration, an adjust member removably attached to the stepped portion and having a lower face placed on a seat rail for adjusting the height between the seat rail and the seat, and vehicle body side fixing members provided on the seat rail for abutting with an abutting portion to fix the adjust member. Upon seat height adjustment, adjustment of the seat height can be carried out simply only by replacing the adjust member to an arbitrary stage of the stepped portion. Further, since the seat height adjustment apparatus is formed from the three parts of the stepped portion, adjust member and vehicle body side fixing member, the number of parts is reduced.