  We study the general requirement for supersymmetric AdS$_6$ solutions in type
IIB supergravity. We employ the Killing spinor technique and study the
differential and algebraic relations among various Killing spinor bilinears to
find the canonical form of the solutions. Our result agrees precisely with the
work of Apruzzi et. al. \cite{Apruzzi:2014qva} which used the pure spinor
technique. We also obtained the four-dimensional theory through the dimensional
reduction of type IIB supergravity on AdS$_6$. This effective action is
essentially a nonlinear sigma model with five scalar fields parametrizing
$\textrm{SL}(3,\mathbb{R})/\textrm{SO}(2,1)$, modified by a scalar potential
and coupled to Einstein gravity in Euclidean signature. We argue that the
scalar potential can be explained by a subgroup CSO(1,1,1)
$\subset\textrm{SL}(3,\mathbb{R})$ in a way analogous to gauged supergravity.
