To provide a plinth block, a foundation, and a base, and a structure and a method of joining the base to a structure body capable of easily connecting in short time the base adjacent to an entrance floor to the structure body such as floor members, edge members, and foundation in an increased airtight state.

The plinth block 10 laid down on the upper end of the base 9 adjacent to the entrance floor 1 and provided between the base 9 and an entrance frame part 6 constructed on the base 9 comprises a plinth block body 14 disposed on the upper surface of the base 9 along the longitudinal direction thereof and a seal material 15 disposed on the plinth block body 14 parallel with each other along the longitudinal direction thereof and closely fitted onto the upper surface of the base 9 and the lower surface of the entrance frame part 6.