  Twisted Lefschetz numbers are extensions of the ordinary Lefschetz numbers
for cohomologies with values in flat bundles. As a generalization of
linearization formula for the ordinary Lefschetz number of a self-map of a
nilmanifold, we show that a twisted Lefschetz number of any self-map of any
infra-solvmanifold is equal to the determinant ${\rm det}(I-A)$ for some matrix
$A$ by using the cohomology of algebraic groups.
