  We present a status report of our calculation of the electromagnetic form
factor of the pion on the PACS-CS gauge field configurations generated using
Iwasaki gauge action and Wilson-clover quark action for 2 + 1 flavors of light
dynamical quarks. The technique of twiseted boundary conditon is employed to
explore the form factor for small momentum transfer. The $q^2$ behavior of the
form factor and its light quark mass dependence is examined.
