  For the space of $(\sigma,\tau)$-derivations of the group algebra $
\mathbb{C} [G] $ of discrete countable group $G$, the decomposition theorem for
the space of $(\sigma,\tau)$-derivations, generalising the corresponding
theorem on ordinary derivations on group algebras, is established in an
algebraic context using groupoids and characters. Several corollaries and
examples describing when all $(\sigma,\tau)$-derivations are inner are
obtained. Considered in details cases on $(\sigma,\tau)-$nilpotent groups and
$(\sigma,\tau)$-$FC$ groups.
