To provide an inertia sensor and a method for reducing an operation error of the inertia sensor, the sensor and the method being configured such that complicated means is not required, and such that, even at the initial use stage in which the temperature characteristic of the sensor is not learned, and even in the case where the sensor is used in an ambient temperature different from the ambient temperature during the previous use of the sensor, an operation error due to an output change caused by a temperature change can be reduced in a relatively simple and highly accurate manner. An inertia sensor 10 is configured by including at least a sensor element 1 for sensing inertia, a signal processing circuit 2, and a memory 3, and is configured such that memory data 8 for estimating a characteristic of the inertia sensor 10 is stored in the memory 3. An angular velocity sensor and an acceleration sensor are included in the category of the inertia sensor 10.