PURPOSE: To provide a glass wool board having thin joints whose strength is ensured and capable of smooth joining, and its molding method.

CONSTITUTION: A fabric 5 forming a facing of one face of a glass wool board is stuck to a bottom face of a glass wool mat 4 and injected from an inlet of a cure furnace together with the glass wool mat 4 along its bottom face so as to be integrated by a thermosetting molding. End parts of flights 2 and 3 form protruding steps 8 and 9 for forming thin joints 6 and 7 at the edges of the board. The sticking range of the fabric 5 on the bottom face of the glass wool mat 4 is limited to a range from the edge of the protruding step 9 to a pressing width W which is not restrained by the protruding step 9.