A mortar shell struck a civilian home in the town of Sheikh Zuweid in the northern part of the region.
Officials blame jihadist militants for the attack.
Their target was apparently a nearby military base, but it struck the home instead.
Militancy in the Sinai region has been a serious concern for Egyptian President Abdel Fattah EL Sisi.
Earlier this month, militants affiliated to ISIL launched a devastating attack on the army in the same city of Sheikh Zuweid.