Zaksullah Khan was killed by unidentified gunmen after he came out from a mosque, after evening prayer, police said.
He was taken to hospital where he succumbed to his injuries.
The reason of shooting is yet to be ascertained, police said, adding that personal enmity may also be a reason behind the shooting.
However, polio workers have long been targeted in the country by Islamist groups including the Taliban militants which claim that the polio immunisation drive is a front for espionage or a conspiracy to sterilise Muslims.