Data indicating a sudden change in a bulk modulus of fuel and data indicating a usage state and a usage environment of an injector as of occurrence of an injection abnormality are stored in EEPROM mounted in the injector. Thus, it can be analyzed whether a cause of a defect such as the injection abnormality is use of inferior fuel based on the data related to the bulk modulus. In addition, it can be analyzed whether the cause of the defect such as the injection abnormality is a severe usage state and a severe usage environment based on the data related to the usage state and the usage environment. Thus, the data useful for analyzing the cause of the defect related to the fuel injection can be provided.