Can I use Bipolar stepper motor driver to drive Unipolar motor in Unipolar configuration ?
It depends on the bipolar motor driver you're using.
A driver chip like the L293D (or various more powerful equivalents) would usually be configured as two full H-bridges to drive two simple DC motors forwards or backwards - or to drive the two coils of a bipolar stepper motor.
However it can be configured as four half-bridge drivers, to independently drive four coils in simple on/off mode. So these could be the four coils of a unipolar stepper. For example there's a description here: http://mechatronics.mech.northwestern.edu/design_ref/actuators/stepper_drive1.html
If on the other hand you are using a ready-made driver that doesn't allow wiring changes, it may not be possible to drive unipolar steppers with it. So if you have a specific driver in mind, I'd recommend first looking for a datasheet, or manufacturer's advice, to see if this is possible.