  The state-of-the-art geometry models of stars/dust suggest that dust
attenuation toward nebular regions ($A_{V,gas}$) is always larger than that of
stellar regions ($A_{V,star}$). Utilizing the newly released integral field
spectroscopic data from the MaNGA survey, we investigate whether and how the
$A_{V,star}/A_{V,gas}$ ratio varies from subgalactic to galactic scales. On a
subgalactic scale, we report a stronger correlation between $A_{V,star}$ and
$A_{V,gas}$ for more active HII regions. The local $A_{V,star}/A_{V,gas}$ is
found to have moderate nonlinear correlations with three tracers of diffuse
ionized gas (DIG), as well as indicators of gas-phase metallicity and
ionization. The DIG regions tend to have larger $A_{V,star}/A_{V,gas}$ compared
to classic HII regions excited by young OB stars. Metal-poor regions with a
higher ionized level suffer much less nebular attenuation and thus have larger
$A_{V,star}/A_{V,gas}$ ratios. A low-$A_{V,gas}$ and
high-$A_{V,star}/A_{V,gas}$ sequence, which can be resolved into DIG-dominated
and metal-poor regions, on the three BPT diagrams is found. Based on these
observations, we suggest that besides the geometry of stars/dust, local
physical conditions such as metallicity and ionized level also play an
important role in determining the $A_{V,star}/A_{V,gas}$. On a galactic scale,
the global $A_{V,star}/A_{V,gas}$ ratio has strong correlations with stellar
mass ($M_*$), moderate correlations with SFR and metallicity, and weak
correlations with inclination and specific SFR. Galaxies with larger $M_*$ and
higher SFR that are more metal-rich tend to have smaller $A_{V,star}/A_{V,gas}$
ratios. Such correlations form a decreasing trend of $A_{V,star}/A_{V,gas}$
along the star-forming main sequence and mass-metallicity relation. The dust
growth process accompanied by galaxy growth might be one plausible explanation
for our observations.
