  We present the result of a Suzaku X-ray spectroscopic observation of the
dwarf nova Z Camelopardalis, which was conducted by chance at the onset of an
optical outburst. We used the X-ray Imaging Spectrometer (a 38 ks exposure) and
the Hard X-ray Detector (34 ks) to obtain a 0.35-40 keV spectrum
simultaneously. Spectral characteristics suggest that the source was in the
X-ray quiescent state despite being in the rising phase of an outburst in the
optical band. The spectrum shows a clear signature of circumstellar absorption
in excess of interstellar absorption and the reprocessed emission features of
Fe fluorescence and Compton scattering. The extra absorption is explained due
to partial coverage by either neutral or ionized matter. We found a spectral
change during the observation, which is attributable only to the change in the
circumstellar absorption. Such an X-ray spectral variation is reported for the
first time in dwarf novae. We speculate that the variation in the circumstellar
absorption is interpreted as a time-varying disk wind or geometrically flaring
disk around the white dwarf during the propagation of a heat wave inward along
the accretion disk at the beginning of the outburst, in which optical outburst
and X-ray quiescent states co-exist.
