  It is well known that the Riemann zeta function can be completed to the
Riemann xi function $\xi(s)$ in the sense that its functional equation has a
higher symmetric form $\xi(1-s)=\xi(s)$. In the previous paper (Tohoku Math. J.
72 (2020), 349--378), we give an explicit formula of functional equations
between local and global zeta functions associated with a homogeneous cone and
with its dual cone. In this paper, we consider a completion of these local zeta
functions and show that, for a certain class of homogeneous cones, the
associated local zeta functions admit a kind of completion forms.
