  We studied effect of non-magnetic and magnetic impurities on
superconductivity in Lu$_2$Fe$_3$Si$_5$ by small amount substitution of the Lu
site, which investigated structural, magnetic, and electrical properties of
non-magnetic (Lu$_{1-x}$Sc$_x$)$_2$Fe$_3$Si$_5$,
(Lu$_{1-x}$Y$_x$)$_2$Fe$_3$Si$_5$, and magnetic
(Lu$_{1-x}$Dy$_x$)$_2$Fe$_3$Si$_5$. The rapid depression of $T_c$ by
non-magnetic impurities in accordance with the increase of residual resistivity
reveals the strong pair breaking dominated by disorder. We provide compelling
evidence for the sign reversal of the superconducting order parameter in
Lu$_2$Fe$_3$Si$_5$.
