  We examine by a perturbation method how the self-trapping of g-mode
oscillations in geometrically thin relativistic disks is affected by uniform
vertical magnetic fields. Disks which we consider are isothermal in the
vertical direction, but are truncated at a certain height by presence of hot
coronae. We find that the characteristics of self-trapping of axisymmetric
g-mode oscillations in non-magnetized disks is kept unchanged in magnetized
disks at least till a strength of the fields, depending on vertical thickness
of disks. These magnetic fields become stronger as the disk becomes thinner.
This result suggests that trapped g-mode oscillations still remain as one of
possible candidates of quasi-periodic oscillations observed in black-hole and
neutron-star X-ray binaries in the cases where vertical magnetic fields in
disks are weak.
