A flat pressure sensor of the invention is prepared by processing a thin film of a polymer material to have plurality of substantially square openings 24. A planar member 22 of the flat pressure sensor thus obtained has a net-like structure including multiple element formation areas 26 and multiple bridging areas 28 that respectively bridge the multiple element formation areas 26. Pressure sensor elements 30 are provided in the multiple element formation areas 26 of the planar member 22. A wiring to the pressure sensor elements 30 is formed on the multiple bridging areas 28. The net-like structure enables the flat pressure sensor to be stretched in diagonal directions without arrangement of the bridging areas 28 and to be deformed to a curved surface. The flat pressure sensor of the invention is thus attached to a curved surface, for example, a spherical surface.