Is it possible to take up any field that is not relevant with my undergraduate degree for earning a graduate degree?

It is a general phenomenon to do a graduation study on the field that is relevant with your undergraduate subjects. However, in case you have studied on allied subjects in your undergraduate classes and wish to enrol for graduating on a particular subject, then it becomes mandatory for you to complete the designated undergraduate courses on that subject in the same institution where you wish to enrol for your graduation degree. Again, in case of admission to professional degree courses such as hotel management or business education, the mentioned rule do not apply. For a business education program, one might require some relevant work experience.