  Radiatively driven transfer flow perpendicular to a luminous disk was
examined under a fully special relativistic treatment, taking into account
radiation transfer. The flow was assumed to be vertical, and the gravity, the
gas pressure, and the viscous heating were ignored. In order to construct the
boundary condition at the flow top, the magic speed above the flat source was
re-examined, and it was found that the magic speed above a moving source can
exceed that above a static source ($\sim 0.45~c$). Then, the radiatively driven
flow in a luminous disk was numerically solved, from the flow base (disk
``inside''), where the flow speed is zero, to the flow top (disk ``surface''),
where the optical depth is zero. For a given optical depth and appropriate
initial conditions at the flow base, where the flow starts, a loaded mass in
the flow was obtained as an eigenvalue of the boundary condition at the flow
top. Furthermore, a loaded mass and the flow final speed at the flow top were
obtained as a function of the radiation pressure at the flow base; the flow
final speed increases as the loaded mass decreases. Moreover, the flow velocity
and radiation fields along the flow were obtained as a function of the optical
depth. Within the present treatment, the flow three velocity $v$ is restricted
to be within the range of $v < c/\sqrt{3}$, which is the relativistic sound
speed, due to the relativistic effect.
