  It has been suggested that cosmic strings produced at a phase transition in
the early universe can be the origin of the extremely high energy cosmic rays
(EHCR) observed by AGASA above 10^20 eV.
  Superheavy cosmic strings with linear mass density of 10^22 g/cm can be
indirectly observed through the gravitational lensing effect the distant
galaxies. The lensing effect by a long straight object can be characterized by
a line of double galaxies or quasars with angular separation of about 5 arcsec.
We have searched for aligned double objects from the archived data taken by the
Subaru Prime Focus Camera (Suprime-Cam). The Suprime-Cam has a great advantage
in observing the wide field of view (30x30 arcmin^2) with high sensitivity
(R<26 400s exposure), so it is suitable for this research.
  In this paper, we describe the result of simulation study for developing the
method of searching the objects lensed by cosmic strings, and present the
observational result obtained by this method.
