A branch connector, comprising: a pair of split housings (16, 30) connected by a connecting portion (46, 47) and being fittable into each other; a contact attached to one of said pair of split housings (16, 30); and a filler filled in said pair of split housings (16, 30), wherein a surface shape of said filler is formed into said pair of split housings (16, 30) such that it corresponds to an inner surface shape of said pair of split housings (16, 30), wherein said filler is made of a material that changes physical properties from a fluid state to an elastic state; and in said fluid state, after said surface shape is formed such that it corresponds to said inner surface shape of said pair of split housings (16, 30), the physical properties change to said elastic state; wherein said filler is made of a material that changes said physical properties from said fluid state to said elastic state by UV irradiation; a pair of elastic first locking portions formed on both right and left sides of an outer peripheral wall of the one of said pair of split housings (16, 30); a pair of second locking portions formed on both right and left sides of an outer peripheral wall of the other of said pair of split housings (16, 30), the pair of second locking portions being formed on the inner surface of the other of said pair of split housings (16, 30); wherein the inner peripheral side of the outer peripheral wall of the other of said pair of split housings (16, 30) is formed of an inner peripheral recess portion that is one-step lower than the outer peripheral wall and the bottom surface of the inner peripheral recess portion is formed of an inner peripheral second opposed surface formed of a plane that is perpendicular to the direction along which the pair of split housings (16, 30) are configured to be fitted; and wherein the filler is configured to come in contact with the inner surface of the pair of first locking portions of the one of said pair of split housings (16, 30); characterized in that the other of said pair of split housings (16, 30) includes a pair of hole portions formed on both right and left edges of the inner peripheral second opposed surface such that each hole portion is adjacent to one of the pair of second locking portions on both right and left sides, wherein each hole portion runs through from the surface of the inner peripheral second opposed surface to the outer surface of the other of said pair of split housings (16, 30); and said surface shape of said filler is formed in a state where said hole portion is closed by placing said pair of split housings (16, 30) on a jig on which a protrusion corresponding to said hole portion is formed. a pair of split housings (16, 30) connected by a connecting portion (46, 47) and being fittable into each other; a contact attached to one of said pair of split housings (16, 30); and a filler filled in said pair of split housings (16, 30), wherein a surface shape of said filler is formed into said pair of split housings (16, 30) such that it corresponds to an inner surface shape of said pair of split housings (16, 30), wherein said filler is made of a material that changes physical properties from a fluid state to an elastic state; and in said fluid state, after said surface shape is formed such that it corresponds to said inner surface shape of said pair of split housings (16, 30), the physical properties change to said elastic state; wherein said filler is made of a material that changes said physical properties from said fluid state to said elastic state by UV irradiation; a pair of elastic first locking portions formed on both right and left sides of an outer peripheral wall of the one of said pair of split housings (16, 30); a pair of second locking portions formed on both right and left sides of an outer peripheral wall of the other of said pair of split housings (16, 30), the pair of second locking portions being formed on the inner surface of the other of said pair of split housings (16, 30); wherein the inner peripheral side of the outer peripheral wall of the other of said pair of split housings (16, 30) is formed of an inner peripheral recess portion that is one-step lower than the outer peripheral wall and the bottom surface of the inner peripheral recess portion is formed of an inner peripheral second opposed surface formed of a plane that is perpendicular to the direction along which the pair of split housings (16, 30) are configured to be fitted; and wherein the filler is configured to come in contact with the inner surface of the pair of first locking portions of the one of said pair of split housings (16, 30); characterized in that the other of said pair of split housings (16, 30) includes a pair of hole portions formed on both right and left edges of the inner peripheral second opposed surface such that each hole portion is adjacent to one of the pair of second locking portions on both right and left sides, wherein each hole portion runs through from the surface of the inner peripheral second opposed surface to the outer surface of the other of said pair of split housings (16, 30); and said surface shape of said filler is formed in a state where said hole portion is closed by placing said pair of split housings (16, 30) on a jig on which a protrusion corresponding to said hole portion is formed.