A network camera 1 comprises a camera block 10 for taking an image, a signal processing unit 20 supplied with an imaging output of the camera block 10, a communication interface unit 30 which connects to an external network to establish communication, a backup memory unit 40 which temporarily stores data to be transmitted to an external device via the communication interface unit 30, a system control unit 50 which controls the above components, and the like. The system control unit 50 monitors the state of the network and stores temporarily the compressed image data to be transmitted to the server in the backup memory unit 40 when a failure occurs in the network, and controls transmission processing such that the compressed image data that has been stored in the backup memory unit 40 is transmitted to the server after the network has recovered.