The North Sinai is the fertile terrain of the Islamist State group (IS) in Egypt. The jihadists have been avenging the overthrow of Islamist elected President Mohamed Morsi in 2013 by current President al-sisi.
The Thursday victim, a 40-year old man, was shot in the neck, in his house in the capital of the province, El-Arish, security officials and the medics said. The militants also torched the house, officials added.
Two other Coptic Christians, a father and son, were found dead on Wednesday behind a school in the provincial capital.
The Christian community, a minority religious group, has been a target for the terrorist group. The group reportedly said on Sunday it would increase attacks against the community.
In December, Egypt mourned the dead of 12 Coptic Christians in Cairo after an IS subside bomber blew himself in a church.