An injector includes a nozzle hole, a metal body including a high pressure passage inside the body, and a fuel pressure sensor attached to the body to detect fuel pressure. The sensor includes a metal flexure element resiliently deformed upon application of fuel pressure to the flexure element, and a sensor element that converts flexure in the flexure element into an electrical signal and outputs the signal as a pressure detection value. The body includes a sensor high pressure passage communicating with the flexure element, and a body side sealing surface on which the flexure element is pressed and closely-attached so that a clearance between the body and the flexure element is metal-to-metal sealed on the sealing surface. Carburizing treatment is performed on at least a part of the body that defines the sensor high pressure passage. The carburizing treatment is not performed on the sealing surface.