A rubber extrusion device includes a head mounted with a die having: an extrusion port variable member disposed at a front end position of an extrusion flow path to move in a direction allowing an area of an extrusion port to change; and a rectifying body that enters and exits the extrusion flow path from a front end side of the extrusion flow path. A rubber extrudate is manufactured by: positioning the extrusion port variable member at a desired position in its movement direction; positioning the rectifying body at a desired position by moving the rectifying body in an extension direction of the extrusion flow path while being in contact with an inner wall of the extrusion flow path; and extruding unvulcanized rubber from the extrusion port by feeding the unvulcanized rubber into the extrusion flow path.