A connector, comprising: a packing which includes: a packing body part formed in an annular shape; at least a pair of ear parts extending outward from the packing body part; and lock receiving parts are provided in the ear parts; and a case which includes: a case body part which is provided with an opening; a packing-mounted part formed in an annular shape which is provided around the opening of the case body part and on which the packing body part is mounted; a flange part which is integrally provided on the case body part to surround the packing-mounted part; and at least a pair of through holes which are formed in the case body part to communicate between a face of the packing-mounted part where the packing body part is mounted and a back face of the flange part, and through which the ear parts are respectively passed; the pair of through holes are formed in side areas of the case body part in the lateral direction being the direction perpendicular to the front-back direction in which a plurality of terminals are aligned; characterized in that at least a pair of locking parts which are provided on the back face of the flange part and with which the lock receiving parts in the ear parts are respectively engaged, the lock receiving parts in the pair of ear parts are formed as through holes, and the pair of locking parts of the case are formed as projections passing the respective through holes, a distance between a pair of the projections is set to be larger than a distance between a pair of the through holes, while the packing is separated from the case, and the packing is configured to be elastically deformed between the pair of through holes, when the packing is mounted on the case, whereby tensile stress occurs in the packing. a packing which includes: a packing body part formed in an annular shape; at least a pair of ear parts extending outward from the packing body part; and lock receiving parts are provided in the ear parts; and a packing body part formed in an annular shape; at least a pair of ear parts extending outward from the packing body part; and lock receiving parts are provided in the ear parts; and a case which includes: a case body part which is provided with an opening; a packing-mounted part formed in an annular shape which is provided around the opening of the case body part and on which the packing body part is mounted; a flange part which is integrally provided on the case body part to surround the packing-mounted part; and at least a pair of through holes which are formed in the case body part to communicate between a face of the packing-mounted part where the packing body part is mounted and a back face of the flange part, and through which the ear parts are respectively passed; the pair of through holes are formed in side areas of the case body part in the lateral direction being the direction perpendicular to the front-back direction in which a plurality of terminals are aligned; characterized in that at least a pair of locking parts which are provided on the back face of the flange part and with which the lock receiving parts in the ear parts are respectively engaged, the lock receiving parts in the pair of ear parts are formed as through holes, and the pair of locking parts of the case are formed as projections passing the respective through holes, a distance between a pair of the projections is set to be larger than a distance between a pair of the through holes, while the packing is separated from the case, and the packing is configured to be elastically deformed between the pair of through holes, when the packing is mounted on the case, whereby tensile stress occurs in the packing. a case body part which is provided with an opening; a packing-mounted part formed in an annular shape which is provided around the opening of the case body part and on which the packing body part is mounted; a flange part which is integrally provided on the case body part to surround the packing-mounted part; and at least a pair of through holes which are formed in the case body part to communicate between a face of the packing-mounted part where the packing body part is mounted and a back face of the flange part, and through which the ear parts are respectively passed; the pair of through holes are formed in side areas of the case body part in the lateral direction being the direction perpendicular to the front-back direction in which a plurality of terminals are aligned; characterized in that at least a pair of locking parts which are provided on the back face of the flange part and with which the lock receiving parts in the ear parts are respectively engaged, the lock receiving parts in the pair of ear parts are formed as through holes, and the pair of locking parts of the case are formed as projections passing the respective through holes, a distance between a pair of the projections is set to be larger than a distance between a pair of the through holes, while the packing is separated from the case, and the packing is configured to be elastically deformed between the pair of through holes, when the packing is mounted on the case, whereby tensile stress occurs in the packing.