A weather strip includes a trim portion that is a substantially U-shaped, that is mounted on a flange portion provided along a door opening circumference portion of a vehicle, and that is equipped with a vehicle outer-sided side wall portion, a vehicle inner-sided side wall portion, and a coupling portion for coupling the side wall portions to each other, and a seal portion including a hollow portion. The seal portion includes a first elongated portion which is elongated to a vehicle outer side from a portion located in a vicinity of a boundary portion between the seal portion and the coupling portion of the vehicle outer-sided side wall portion, a second elongated portion which is elongated to a vehicle outer side from a portion located in a vicinity of a tip portion of the vehicle outer-sided side wall portion, and an expanded portion having substantially an arc shape.