A coolant passage structure for an internal combustion engine includes a coolant communication member. The coolant communication member includes a centrifugal water pump, a housing portion, a scroll portion, a second coolant passage portion, a first coolant passage portion, a direction of a center line of the second coolant passage portion, and a rib. The first coolant passage portion includes a downstream region connected to an upstream region of the second coolant passage portion. A direction of a center line of the first coolant passage portion is parallel to a direction of a rotation shaft of the centrifugal water pump. The direction of the center line of the second coolant passage portion is orthogonal to the direction of the center line of the first coolant passage portion. The rib is disposed on an internal circumferential surface of the first coolant passage portion.