A joint box achieve both ease of sealability and construction, and to provide a construction method using the joint box. A joint box 10, a plurality of cable connection portions which end is connected the Ca to Cd Bab1～Bab3, a joint box 10 to to insulating protective housing the Bcd1～Bcd3, configured in a cylindrical shape a body portion 40, a cable Ca~Cd can be inserted opening area in the one axial end of the body portion 40 first cover portion having a part (cable entry hole 64a-64d) (bottom lid 60), the second cover portion which is linkable separate configuration a body portion 40 which has a closure surface for closing the one axial end side of the body portion 40 opposite to the other axial end (the bottom lid portion 20) having. .Field