  We investigate the torus size -- luminosity relation of Type 1 AGNs based on
the reverberation-mapping analysis using the light curves of the optical
continuum and the IR continuum obtained with the W1 and W2-bands of the
Wide-field Infrared Survey Explorer (WISE) survey. The final sample consists of
446 and 416 AGNs, respectively, for W1 and W2-band light curves, covering a
large dynamic range of bolometric luminosity from $10^{43.4}$ to $10^{47.6}$
$erg \, s^{-1}$, which show reliable lag measurements based on our quality
assessment analysis. After correcting for the accretion disk contamination in
the observed IR flux, we constrain the torus size ($R_{dust}$) and AGN
bolometric luminosity ($L_{bol}$) relationship with the best-fit slope of 0.39
(0.33) for the W1- (W2-) band, which is shallower than expected from the dust
radiation equilibrium model. By combining the previous K-band lag measurements,
we find that the measured torus size depends on the observed wavelength of the
dust radiation, as $R_{dust,K}:R_{dust,W1}:R_{dust,W2}$ = 1.0:1.5:1.8
($R_{dust} \, \propto \, \lambda^{0.80}$) at $L_{bol}$ = $10^{46} \, erg \,
s^{-1}$, confirming a stratified structure of the torus, where
wavelength-dependent emissions originate from distinct regions of the torus. By
investigating the deviation from the best-fit torus size -- luminosity
relation, we find a moderate correlation between the offset from the
$R_{dust}$--$L_{bol}$ relation and Eddington ratio. This suggests a possible
influence of the Eddington ratio on the observed flattening of the
$R_{dust}$--$L_{bol}$ relationship.
