Hello Bumang Nangba!

NO, it is not necessary to give NATA exam for admission in B.arch college in India. The other entrance exam that you can give for getting admission in B.arch college in india is JEE main paper 2(B.arch). But my suggestion is try to attempt both the paper, NATA as well as JEE main paper 2 because in some colleges the NATA is compulsory and if you did not perform well in NATA you might still get an admission based on your JEE main paper 2 as it is considered the top entrance exam for any engineering college.

So attempt both the exams get a good score and select a good B.arch college and enjoy!

Good Luck!