To provide an expansion joint material formed of a core material covered with a cap member which is rarely detached therefrom.

In an expansion joint material 1 formed of a core material 2 to be fixed to a skeleton and a cap member 3 covering the same, the cap member 3 has a top board 31, side wall portions 32 hanging therefrom, and engaging portions 33 each sideward protruding from a lower edge of the side wall portion 32. The thus formed cap member 3 is attached to the core material 2 which is fixed to the skeleton via a pedestal member 5, and fastening plates 4 each having an engaging edge 41 for engaging with the engaging portion 33 and a nail portion 43 for being driven into the core material 2 are arranged on both sides of the core material 2 at appropriate intervals, whereby the cap member 3 is engaged with the core material 2.