To provide a joint material which can easily and surely seal a joint part without hindering movements of a male-female fitting part by thermal expansion and contraction of a frame body, and can keep the part between an underlayer and the frame body, and the joint part clean for a long period of time.

The joint material comprises a belt-like surface covering part covering the joint part, a post part extending downward from a rear surface of the surface covering part, and an elastic locking part projecting from both side faces of the post part in a direction of the width of the surface covering part and being elastically in contact with both side faces of a unit floor material. When the maximum width of the joint part is defined as W1, the minimum width thereof as W2, the depth of the joint part as H1, the width of the surface covering part as w1, the length of the post part in the width direction of the surface covering part as w2, the width-directional length of the elastic locking part in a no-load condition as w3, and the length of the post part as h1, the relationships of w1W1, w3W1, w2W2, and h1H1 are satisfied.