  A moderately deep survey of stellar maser sources toward the Galactic center
has been made in the SiO J=1-0 v=1 and v=2 transitions (~ 43 GHz) with the
Nobeyama 45-m telescope of a beam size of about 40". At the Galactic center
(Sgr A*), 7 (4 new) SiO maser sources were detected in one beam. In order to
investigate the spatial distribution of SiO maser sources, we have also
observed the offset positions by +- 40" in Galactic longitude from the Galactic
center. In total, 7 (4 new) SiO maser sources were detected at the offset
positions. Taking into account the shorter integration time at the offset
positions, we find that the surface number density of SiO maser sources is
nearly constant at the Galactic center. The number density of SiO maser sources
is found to be an order of magnitude higher than the density of OH 1612 MHz
objects. A radial-velocity gradient in Galactic longitude was not detected.
These facts indicate that the SiO maser sources seen toward the Galactic center
are mostly associated with the stellar population of a Galactic stellar nuclear
disk of more than a few arc minute radius.
