  We study a hierarchical triple system with the Kozai-Lidov mechanism, and
analyse the cumulative shift of periastron time of a binary pulsar by the
emission of gravitational waves. Time evolution of the osculating orbital
elements of the triple system is calculated by directly integrating the
first-order post-Newtonian equations of motion. The Kozai-Lidov mechanism will
bend the evolution curve of the cumulative shift when the eccentricity becomes
large. We also investigate the parameter range of mass and semi-major axis of
the third companion with which the bending of the cumulative-shift curve could
occur within 100 years.
