  The path-integral measure of linearized gravity around a saddle-point
background with the cosmological term is considered in order to study the
conformal rotation prescription proposed by Gibbons, Hawking and Perry. It is
also argued that the most generally used measure, i.e., the covariant
path-integral measure, does not give us a one-loop partition function which the
only physical variables contribute and that its path integral fails to keep the
cancellation of contributions between the Faddeev-Popov ghosts and the
unphysical variables of the linearized gravitational field, although it has a
coordinate invariant measure. In de~Sitter spacetime, it is shown that the
uncancellation factor can be understood as a nontrivial (anomalous) Jacobian
factor under the transformation of the path-integral measure from covariant one
to canonical one.
