Provided are a blur detection device, an imaging device, a lens device, an imaging device main body, a blur detection method, and a blur detection program capable of appropriately detecting blurring of an imaging device. An angular velocity of a digital camera and a posture of the digital camera with respect to an Earth's rotation axis are detected. An Earth's rotation angular velocity component superimposed on a detection result of the angular velocity is calculated. The Earth's rotation angular velocity component is subtracted from the detection result of the angular velocity, and a blur amount of the digital camera is calculated based on the subtracted angular velocity.