A height adjustment device and a swivel device for a vehicle seat are configured to adjust seat height and swivel the vehicle seat. The height adjustment device includes a first reduction gear device disposed at a bottom of the vehicle seat and configured to increase output torque of a first motor and a lifting device engaged with the first reduction gear device and configured to move the seat upwards or downwards, and the swivel device includes a motor driving unit disposed at a bottom of the height adjustment device and a second reduction gear device configured to increase output torque of the motor driving unit, thereby making it possible not only to selectively perform seat height adjustment and swivel operation, but also to perform a monopost function of the seat in a state in which the height adjustment device and the swivel device are stacked in a vertical direction.