1. An image-capturing method of an image-capturing device for recording still images or moving images as image-captured images of a subject, comprising the steps of: an image-capturing step executing image-capturing or recording of an image-captured image of an object with a timing specified by a shutter operation or a shutter operation program; and a trigger transmitting step (a) automatically transmitting to an external image-capturing device at least one additional information related to the image-capturing device and a trigger signal when the shutter operation or shutter operation program is executed and (b) instructing image-capturing or recording of an image-captured image of a scene including the object to the external image-capturing device with said timing.