To provide a junction structure of a heat insulation panel, capable of suppressing the decline of airtightness and heat insulation of a junction (joint part) due to the peeling and position deviation of a frame material in the junction (joint part) of the heat insulation panel.

The junction structure of the heat insulation panel includes: a pair of upper and lower surface plates 5 and 6; a frame material 7 interposed between side parts of the upper and lower surface plates; a heat insulation core material 8 filled inside a space formed by the upper and lower surface plates and the frame material 7; and an attaching washer 10 embedded inside the heat insulation core material 8 in the state of being abutted to the inner surface of the upper surface plate 5. An end part bend piece part 21 connected to the frame material 7 is provided on the side part of the lower surface plate 6, and a fitting recessed groove 20 turning inward in the longitudinal direction is formed at the end part bend piece part 21. At the attaching washer 10, a locking piece 16 which is inserted between the fitting recessed groove 20 and the surface part of the lower surface plate 6 and is capable of being engaged with the fitting recessed groove 20 is formed. When joining the heat insulation panels with each other, an incombustible junction member 30 is fitted inside the fitting recessed grooves 20 of both the heat insulation panels to be joined, and both the heat insulation panels are joined.