  We present the earliest optical imaging observations of GRB 030329 related to
SN 2003dh. The burst was detected by the HETE-2 satellite at 2003 March 29,
11:37:14.67 UT. Our wide-field monitoring started 97 minutes before the trigger
and the burst position was continuously observed. We found no precursor or
contemporaneous flare brighter than $V=5.1$ ($V=5.5$) in 32 s (64 s) timescale
between 10:00 and 13:00 UT. Follow-up time series photometries started at
12:51:39 UT (75 s after position notice through the GCN) and continued for more
than 5 hours. The afterglow was $Rc= 12.35\pm0.07$ at $t=74$ min after burst.
Its fading between 1.2 and 6.3 hours is well characterized by a single
power-law of the form $f{\rm(mJy)} = (1.99\pm0.02{\rm (statistic)}\pm0.14{\rm
(systematic)}) \times (t/1 {\rm day})^{-0.890\pm 0.006 {\rm (statistic)}\pm
0.010 {\rm (systematic)}}$ in $Rc$-band. No significant flux variation was
detected and upper limits are derived as $(\Delta f/f)_{\rm RMS} = 3-5$% in
minutes to hours timescales and $(\Delta f/f)_{\rm RMS} = 35-5$% in seconds to
minutes timescales. Such a featureless lightcurve is explained by the smooth
distribution of circumburst medium. Another explanation is that the optical
band was above the synchrotron cooling frequency where emergent flux is
insensitive to the ambient density contrasts. Extrapolation of the afterglow
lightcurve to the burst epoch excludes the presence of an additional flare
component at $t<10$ minutes as seen in GRB 990123 and GRB 021211.
