  We have performed the monitoring observations of flux density of Sagittarius
A* at short millimeter wavelengths (100 and 140 GHz bands) on seven years in
the period from 1996 to 2003 using the Nobeyama Millimeter Array (NMA). We
found intra-day variation of Sgr A* in March 2000 flare. The flux density at
the peak of the flares increases 100-200 % at 100 GHz and 200-400 % at 140 GHz
($?Delta S/S$), respectively. The two-fold increase timescale of the flare is
estimated to be about 1.5 hours at 140 GHz. The intra-day variation at
mm-wavelengths has similar increase timescale as those in the X-ray and
infrared flares but has smaller amplitude. This short timescale variability
suggests that the physical size of the emitting region is smaller than 12 AU
$?approx$ 150 Rs). The decay timescale of the flare was at most 24 hours. Such
a light curve with rapid increase and slow decay is similar to that often
observed in outburst phenomena with ejections.
