The purpose of the present invention is to provide: a pressure-sensing element with a novel structure, said pressure-sensing element measuring the pressure inside an extracorporeal circulation circuit without coming into contact with blood or air, wherein coagulation of blood is better suppressed by minimizing the retention of blood as a result of improving the flow of blood inside the pressure-sensing element and a blood circuit and a blood purification apparatus provided with the pressure-sensing element. The present invention provides a pressure-sensing element for an extracorporeal circulation circuit for measuring pressure inside an extracorporeal circulation circuit that performs extracorporeal treatment of blood, and is provided with: a chamber member provided with a fluid chamber that has a deforming surface deformed by the pressure inside the extracorporeal circulation circuit, a fluid inlet, and a fluid outlet, and that allows the blood to flow in and out a fluid inlet joint for linking the fluid inlet to the extracorporeal circulation circuit and a fluid outlet joint for linking the fluid outlet to the extracorporeal circulation circuit. Flow passages inside the fluid inlet joint and the fluid outlet joint widen in a cone shape toward the fluid chamber.本發明之目的在提供具有新穎構造的壓力檢出體、及具備此壓力檢出體的血液回路及血液淨化裝置,該壓力檢出體係在測量體外循環回路內的壓力而血液不會和空氣接觸的壓力檢出體中,藉由改善壓力檢出體內部的血流以抑制血液的滯留,且更進一步抑制血液的凝固。本發明提供的體外循環回路用壓力檢出體係用以測量執行血液體外處理的體外循環回路內之壓力,具備:室構件,具有會因上述體外循環回路內的壓力而變形的變形面、以及液體流入口及液體流出口,且具備供上述血液流入及排出的液體室;液體流入口接頭,用於藉管子使上述液體流入口與上述體外循環回路連通;及液體流出口接頭,用於藉管子使上述液體流出口與上述體外循環回路連通,其中,上述液體流入口接頭及上述液體流出口接頭的內部流路係朝向上述液體室方向擴開成錐台狀。1‧‧‧壓力檢出體5‧‧‧液體室6‧‧‧壓力測量裝置7‧‧‧空氣室8‧‧‧變形面9‧‧‧室構件10‧‧‧液體流入口接頭11‧‧‧液體流出口接頭12‧‧‧液體室內側隅部13‧‧‧液體室內側隅部14‧‧‧液體室內側隅部
