  We discuss the possibility of detecting the presence of primordial black
holes (PBHs), such as those that might account for galactic dark matter, using
modification of pulsar timing residuals when PBHs pass within ~1000 AU and
impart impulse accelerations to the Earth. With this technique, PBHs with
masses around 10^{25} g (~0.1 lunar mass) can be detected. Currently, the
constraints on the abundance of such dark matter candidates are weak. A 30
year-long monitoring campaign with the proposed Square Kilometer Array (SKA)
can rule out a PBH fraction more than ~1/10 in the solar neighborhood in the
form of dark matter with mass ~10^{25} g.
