To provide a joint material which is capable of surely and nicely sealing (closing) a gap including a corner part with one piece of the joint material.

The joint material 20 is attached to a gap between a flange portion 14a and a front wall face 11 or the like adjacent to the flange portion 14a. The joint material is formed of a surface seal portion 21 installed along the surface side portion of the flange portion 14a, and an insertion portion 22 extending from the surface seal portion 21 toward the inner part of the gap and having a recess 25 formed on the flange portion 14a side. In addition, the joint material 20 is made of a thermoplastic resin, and a corner part C is formed through a step of forming notched portions (26a, 26b), a step of bending, and a step of heating to a temperature equal to or above a softening point.