  Chiral topological semimetals host multifold degenerate band crossing points
under the protection of crystalline symmetries. In this paper, we suggest that
the recently discovered chiral topological semimetals in space group 198, parts
of which are superconducting upon doping, can be new candidates of time
reversal invariant topological superconductors. By investigating the Fermi
surfaces around the band crossing points that carry nonzero Chern numbers, we
clarify how the nontrivial topology of chiral topological semimetals affects
their superconducting state and show the existence of topological
superconductivity in $s_\pm$-wave pairing with surface Majorana fermions. We
further demonstrate that the topological superconductivity is favored by the
inter-unit-cell phonon-mediated electron-electron interaction.
