  We report MAXI and Swift observations of short-term spectral softenings of
the galactic black-hole X-ray binary Swift J1753.5-0127 in the low/hard state.
These softening events are characterized by a simultaneous increase of soft
X-rays (2-4 keV) and a decrease of hard X-rays (15-50 keV) lasting for a few
tens of days. The X-ray energy spectra during the softening periods can be
reproduced with a model consisting of a multi-color disk blackbody and its
Comptonized component. The fraction of the Comptonized component decreased from
0.30 to 0.15 when the spectrum became softer; meanwhile the inner disk
temperature (Tin) increased from 0.2 to 0.45 keV. These results imply that the
softening events are triggered by a short-term increase of the mass accretion
rate. During the observed spectral softening events, the disk flux (F) and Tin
did not obey the relation: F is proportional to Tin^4, suggesting that the
inner disk radius does not reach the innermost stable circular orbit.
