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.La présente invention vise à proposer un élément de détection de pression ayant une nouvelle structure, ledit élément de détection de pression mesurant la pression à lintérieur dun circuit de circulation extracorporelle sans entrer en contact avec le sang ou lair, la coagulation du sang étant mieux supprimée en réduisant au minimum la rétention de sang suite à lamélioration du débit sanguin à lintérieur de lélément de détection de pression et un circuit sanguin et un appareil de purification de sang comprenant lélément de détection de pression. La présente invention concerne un élément de détection de pression pour un circuit de circulation extracorporelle pour mesurer la pression à lintérieur dun circuit
