the like further a bracket 12 for mounting the washer tank 10 at a vehicle body which serves as an auxiliary part auxiliary body is fixed integrally to a side wall of the washer tank 10 the tank main body 10a fig3 shows schematically the structure of a blow molding machine 20 which is used at the time of manufacturing the washer tank 10 the blow molding machine 20 includes a die head 22 and a resin parison p serving as a molding material can be extruded therefrom a blowing device 24 is disposed directly below the die head 22 a blow pin 26 is stood upright at the blowing device 24 and blows air to the resin parison p the resin parison p can be thereby expanded a pair of segmental molding dies 28 and 30 are disposed on both sides of the resin parison p which has been extruded from the die head 22 the molding die 28 is fixed to a mount 32 and the molding die 30 is fixed to a mount 34 and further the mount 32 is fixed to the distal end portion of a pair of guide rails 36 and the mount 34 is fixed to the distal end portion of a.