To provide an open ceiling structure, which can be executed simply and in which heat-insulating performance can be ensured for a prolonged term.

In the open ceiling structure, a plurality of runner fixtures 2 are installed to the lower flange h1 of a steel-framed beam H in an upper floor at intervals, and runners 3 are fixed extending over these runner fixtures 2. An open ceiling substrate 4 is fastened onto the upper flange h2 of the steel- framed beam H in a lower floor while wooden bars 5 are fixed onto the open ceiling substrate 4 in conformity with the fixed places of the runners 3, a plurality of fixtures 6 are fastened onto the wooden bars 5 at intervals, the upper ends of heat-insulating interior wall substrate panels 7 are inserted to the runners 3 and the lower-end section rear faces of the substrate panels 7 are abutted against the fixtures 6, and the fixtures 6 are folded back and fixed onto the heat-insulating interior wall substrate panels 7.