A method of creating a privacy mask from an image imaged by an imaging device in which a rotation axis of a camera and a center of a lens do not match includes measuring a distance from the camera to an object in a first imaging condition; creating a first mask for the object, and storing the distance together with the first mask; and creating a second mask for the object in a second imaging condition and correcting a position of the second mask using the first mask and the distance, wherein an imaging angle of the camera the first imaging condition is same as the imaging angle of the camera in the second imaging condition, and wherein a position of the lens in the first imaging condition is reversed around the rotation axis from a position of the lens in the second imaging condition.