I am completed Three years Diploma in computer Engineering. Now I am interested in CCNA so what is the scope of CCNA regarding job?

CCNA is a foundation exam and provides a good, basic understanding of networking and the OSI model. It could also lead to other more advanced Cisco exams. It may be a highly valued check mark on a resume but it is also a money making scheme by Cisco, since you have to renew every 2 years or take an advanced exam and pass it to maintain your CCNA.