A power seat driving apparatus for a vehicle includes a moving unit and a decelerating mechanism, wherein the decelerating mechanism includes a driving gear to which a driving force is inputted, a driven gear engaged with the driving gear so as to be rotatably driven by the driving gear while decelerating a rotational speed of the driving force transmitted thereto, and a housing, at least one of the driving gear and the driven gear includes a shaft portion and a gear portion including a tooth portion, which engages with a tooth portion of the other one of the driving gear and the driven gear, an annular recessed portion is formed at a stepped portion between the gear portion and the shaft portion, the annular recessed portion, and the housing includes a bearing bore having a bearing surface and an annular protruding portion, which is fitted into the annular recessed portion.