PURPOSE: To provide a wall material assembling structure capable of strongly assembling wall materials by the fitting and engagement of the protruding part of one of them and the through-hole of the other one of them.

CONSTITUTION: In a wall material assembling structure, two wall materials formed by blow molding are assembled so that the end edges of them are mutually meshed so as to cross each other at an almost right angle. An outward protruding part 11 is provided to the end edge of one wall material 2 and the through-hole 14 fitted to and engaged with the protruding part 11 of one wall material 2 is provided to the end edge of the other wall material 3. The parting line at the time of blow molding of one wall material 2 is formed so as to pass the leading end edge of the protruding part 11 to make the leading end edge of the protruding part thick.