A stem is installed to an injector body and is resiliently deformable upon receiving a pressure of high pressure fuel conducted through a high pressure passage of the injector body. A strain gauge is installed to the stem to sense a strain generated in the stem. A molded IC device executes an amplifying operation, which amplifies a signal received from the strain gauge. The stem, the strain gauge and the molded IC device are integrally assembled together to form a fuel pressure sensing unit, which is installed to the injector body by threadably fastening a threaded portion, which is formed at the stem, to the injector body.