PURPOSE: To provide a joint structure between honeycomb panels which is constituted to realize a joint having stable rigidity and strength and simplify and facilitate a construction work.

CONSTITUTION: A joint structure is related to a joint structure between honeycomb panels 1 and 2 wherein skin plates 9 and 10 are joined with the two opening end faces of a honeycomb core 11. Coupling end parts 3 and 4, protruded from the end faces of only the skin plates 9 of two honeycomb panels 1 and 2, are intercoupled in a butt state through a hat-form material 14 in such a state that at least surfaces on one side are positioned approximately flush with each other. The hat-form shape 14 comprises a top plate 15; a base sheet plate 16; and two side plates 17, a square hollow space A is formed in the interior, and flange plate parts 18 are formed in such a state to protrude from a base plate part 16 in the direction of two sides. The top plate part 15 is joined from the inner side with one protruding skin plate 9 of the two honeycomb panels 1 and 2 and the flange plate part 18 is joined from the outside with the other skin plates 10 of the honeycomb panels 1 and 2.