An air passage opening and closing device has: a case defining an air passage; and a slide door provided with a door body that has a plate shape, the slide door slidably disposed in the case and opening or closing the air passage. The case is provided with a case-side sealing surface that is in contact with the door body when the slide door is located to close the air passage. The door body is provided with a rib that protrudes toward an upstream side in a flow direction of air and extends in a moving direction of the slide door.