  Monte Carlo simulation is one of the best tools to study the complex spectra
of Compton-thick AGNs and to figure out the relation between their nuclear
structures and X-ray spectra. We have simulated X-ray spectra of Compton-thick
AGNs obscured by an accretion torus whose structure is characterized by a
half-opening angle, an inclination angle of the torus relative to the observer,
and a column density along the equatorial plane. We divided the simulated
spectra into three components: one direct component, an absorbed reflection
component and an unabsorbed reflection component. We then deduced the
dependencies of these components on the parameters describing the structure of
the torus. Our simulation results were applied to fit the wide-band spectrum of
the Seyfert 2 galaxy Mrk 3 obtained by $Suzaku$. The spectral analysis
indicates that we observe the nucleus along a line of sight intercepting the
torus near its edge, and the column density along the equatorial plane was
estimated to be ~10^24 cm^-2. Using this model, we can estimate the
luminosities of both the direct emission and the emission irradiating the
surrounding matter. This is useful to find the time variability and time lag
between the direct and reflected light.
