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We report results from a Suzaku observation of the narrow-line Seyfert 1 NGC4051. During our observation, large amplitude rapid variability is seen and theaveraged 2--10 keV flux is 8.1x10^-12 erg s^-1 cm^-2, which is several timeslower than the historical average. The X-ray spectrum hardens when the sourceflux becomes lower, confirming the trend of spectral variability known for manySeyfert 1 galaxies. The broad-band averaged spectrum and spectra in high andlow flux intervals are analyzed. The spectra are first fitted with a modelconsisting of a power-law component, a reflection continuum originating in coldmatter, a blackbody component, two zones of ionized absorber, and severalGaussian emission lines. The amount of reflection is rather large (R ~ 7, whereR=1 corresponds to reflection by an infinite slab), while the equivalent widthof the Fe-K line at 6.4 keV is modest (140 eV) for the averaged spectrum. Wethen model the overall spectra by introducing partial covering for thepower-law component and reflection continuum independently. The column densityfor the former is 1x10^23 cm^-2, while it is fixed at 1x10^24 cm-2 for thelatter. By comparing the spectra in different flux states, we identify thecauses of spectral variability. (abridged)

X-Ray Spectral Variability of the Seyfert Galaxy NGC 4051 Observed with Suzaku