  We found superconductivity in CaSb$_2$ with the transition temperature of 1.7
K by means of electrical-resistivity, magnetic-susceptibility, and
specific-heat measurements. This material crystallizes in a nonsymmorphic
structure and is predicted to have multiple Dirac nodal lines in the bulk
electronic band structure protected by symmetry even in the presence of
spin-orbit coupling. We discuss a possible topological superconductivity for
the quasi-2-dimensional band originating mainly from one of the antimony sites.
