  The Berry phase and curvature are studied for the Dirac nodal line semimetal
of single-component molecular conductor [Pd(dddt)$_2$]. Using two-band model on
the basis of a tight-binding model, it is shown that the Berry curvature,
$\bm{B}(\bm{k})$, exists along a loop of the nodal line, on which the Berry
phase is obtained from surface integral of $\bm{B}(\bm{k})$. The Berry phase,
which is called Zak phase, is also calculated from one-dimensional integral of
the Berry connection along a line between two equivalent points of boundaries
of Brillouin zone. The possible experiment is discussed in terms of the Berry
phase.
