To provide a floor heating structure by which a PTC conductive flat heater can be protected against damage when a floor finishing material is repaired or replaced.

A heat insulating material 4 is bonded S1 and laid on the floor face of a concrete slab 5. The PTC conductive flat heater 2 is bonded S2 and fixed on the heat insulating material 4. A protection sheet 3 is bonded S5 and fixed on the PTC conductive flat heater 2. A heating floor 6 is formed by bonding S3 and fixing the floor finishing material 1 on the protection sheet 3. The bonding S5 holding force of the protection sheet 3 is set weaklier than the bonding holding force of upper/lower insulating films 2a, 2b in the PTC conductive flat heater 2 so as not to damage the PTC conductive flat heater 2 when the floor finishing material 1 is repaired or replaced. A part of the bonding S5 layer of the protection sheet 3 is left on the upper face of the PTC conductive flat heater 2 when the floor finishing material 1 is peeled off. Therefore, the protection sheet can be bonded again.