A fluid pressure sensor apparatus includes one or a plurality of fluid pressure sensor elements. Each fluid pressure sensor element comprises a flat hollow structure which extends transverse to the direction of flow of a fluid. An upstream chamber is open through dynamic pressure measuring holes which extend in the direction of the flow, and a downstream chamber is open through static pressure measuring holes which extend transverse to the flow direction. The upstream chamber acts to average the dynamic pressure and the downstream chamber measures static pressure. An auxiliary ridge-like member is located downstream of the static pressure measuring holes.