This invention has as its object to integrate and simplify a communication interface, and to attain a size reduction of a camera housing and a cost reduction. To accomplish this, a digital camera transfers a control signal that controls the operation of at least one strobe device, and an image signal output from an image sensing means via a single USB cable. Upon making an image sensing operation that requires strobe emission of the strobe device, transfer of the image signal is suspended, and a control signal for the strobe device is preferentially transferred.