Hello frens,
I just trying to apply to new job for same work what i am doing. New employer where i am about to apply is asking for my latest paystub to see what i am getting so that they will check my pay and decide salary accordingly.

Is this a normal thing or it is illegal?

What can be the response to this new employer. I know they are trying to pay as low as possible.

It's normal for most of the companies. While negotiating, you can mention that you were getting raise by minimum 15% and youur new salry should be around 30% more than your old company.. You can communicate with your new HR. Share your updates so that we can provide more feedback.
Goodluck

I know few companies which did that. At my work, the range for my position is 6500 to 9500.
So, if I ask for anything greater than the starting range, then they would ask for my pay stub and possibly last year's gross income. If last year's gross income is higher than what they are offering, then they would try to match or go over what they are initially offering.