  For the last few decades, researchers have been intrigued by multipolar
ordering phenomena while looking for the related quantum criticality in the
heavy-fermion Kondo system Ce$_{1-x}$La$_{x}$B$_6$. However, critical phenomena
induced by substitution level ($x$), temperature ($T$), and magnetic field
($B$) are poorly understood despite a large collection of experimental results
is available. In this work, we present $T$-$B$, $x$-$T$, and $x$-$B$ phase
diagrams of Ce$_{1-x}$La$_x$B$_6$ ($\mathbf{B}\parallel[110]$). These are
completed by analyzing heat capacity, magnetocaloric effect (MCE), and elastic
neutron scattering. A drastic increase of the Sommerfeld coefficient
$\gamma_0$, which is estimated from the heat capacity down to 0.05 K, is
observed with increasing $x$. The precise $T$-$B$ phase diagram which includes
an unforeseen high-entropy region is drawn by analyzing the MCE for the first
time in Ce$_{1-x}$La$_x$B$_6$. The $x$-$B$ phase diagram, which supports the
existence of a QCP at $x>0.75$, is obtained by the same analysis. A detailed
interpretation of phase diagrams strongly indicates positive correlation
between the fluctuating multipoles and the effective electron mass.
