Chief Draftsman of the Constitution in the Constituent Assembly was S.N. Mukherjee.

Explanation:
The Constituent Assembly was formed in 1946 to draft the Constitution of India. The drafting committee was appointed on August 29, 1947, with Dr. B.R. Ambedkar as the Chairman.

One of the members of the drafting committee was S.N. Mukherjee, who was also the Chief Draftsman of the Constitution. He played a vital role in drafting the Constitution and was responsible for the language and phrasing used in the final document.

Mukherjee was a prominent lawyer and jurist who had served as the Advocate General of Bengal. He had also been a member of the Central Legislative Assembly and the Constituent Assembly. His expertise in constitutional law and his knowledge of parliamentary procedures were valuable in the drafting process.

Mukherjee worked closely with Dr. Ambedkar and the other members of the drafting committee to create a document that reflected the aspirations of the people of India. He ensured that the language used in the Constitution was clear and unambiguous, and that the provisions were consistent with the principles of democracy and justice.

In conclusion, S.N. Mukherjee was the Chief Draftsman of the Constitution in the Constituent Assembly and played a significant role in the drafting of the Constitution. His expertise and knowledge were instrumental in creating a document that has stood the test of time and has become the cornerstone of Indian democracy.