An omnidirectional camera having a camera for acquiring a digital image, an image data processing device for compressing a signal output from the camera and an external memory is disclosed. In the omnidirectional camera, a writing changeover unit accumulates signals output from a signal processing unit in one of a set of first internal memories until data is accumulated to a predetermined amount. When the data is accumulated to a predetermined amount, the writing changeover unit changes destinations and accumulates signals output from the signal processing unit in the other of the set of first internal memories. The signal is output to a data converting unit from the first internal memory where accumulation reaches the predetermined amount, and the data conversion unit compresses and converts an inputted signal to an image signal and the image signal is inputted to the external memory by an input/output control unit.