  We report on the Fermi surfaces and superconducting parameters of CaSb$_2$
single crystals (superconducting below $T_{\text{c}}\sim 1.8~\text{K}$) grown
by the self-flux method. The frequency of de-Haas-van-Alphen and
Shubnikov-de-Haas oscillations evidences a quasi-two-dimensional (quasi-2D)
Fermi surface, consistent with one of the Fermi surfaces forming Dirac lines
predicted by first-principles calculations. Measurements in the superconducting
state reveal that CaSb$_2$ is close to a type-I superconductor with the
Ginzburg-Landau (GL) parameter of around unity. The temperature dependence of
the upper critical field $H_{\text{c2}}$ is well described by a model
considering two superconducting bands, and the enhancement of the effective
mass estimated from $H_{\text{c2}}(0~\text{K})$ is consistent with the quasi-2D
band observed by the quantum oscillations. Our results indicate that a quasi-2D
band forming Dirac lines contributes to the superconductivity in CaSb$_2$.
