Hey Jyoti,
Both Interior Designing and Fashion Design are equally good and can'y be measured on any scale. You can earn well in both but there is no guarantee which will pay you more. Both Interior Designing and Fashion Designing are lucrative and most sought- after proffessions. The competition is tough as the creative and work efficiency of the market is expanding every minute. Having  good communication skills and creative approach will help you thrive in these industry but cannot vouch for " a good pay". Moreover,you cannot(should not) start off on a new journey by taking into consideration just monetary aspects. The pay might be initially low but over the time,with your dedication and hardwork you will earn good. So first off,be patient and be sure of your calling. Make opportunities come your way and just for once work for the sake of learning something.
Hope this helps.
Good luck.

Hello Jyoti,

Interior design is a branch of design that covers the designing of the interiors of a room or building. It includes the development of a concept, up to the actual execution of the design. Your degree will expand your understanding of the human need, user experience, site context, and culture.

Fashion designers create original clothing, accessories, and footwear. They sketch designs, select fabrics and patterns, and give instructions on how to make the products they design.

Both are totally different fields with different requirements. If you have a good knowledge of that field then you can earn a good amount of money.

Hope it helps you

Thank you