Magsi was attacked while he was on a door-to-door campaign. Three others were injured in the attack. They were taken to a nearby hospital, police said.
The Election Commission deferred polls in the area and said the schedule for the election in Jhal Magsi would be announced later.
Over the past few days, the banned Pakistani Taliban and other groups have targeted campaign offices and election meetings across the country.
More than 40 people had been killed and dozens injured in 26 bomb blasts in Balochistan, Khyber-Pakhtunkhwa and Sindh provinces since campaigning began for the May 11 polls.