An image signal processing device for processing an image signal transmitted from an imaging unit by radio is provided. The image signal processing device is provided with at least one antenna that receives the image signal transmitted from the imaging unit by radio, a substrate, and a plurality of 2D-DST elements arranged on the substrate. The plurality of 2D-DST elements include a plurality of receiving elements each of which includes a processing unit having functions of receiving the image signal and processing the received image signal. The plurality of receiving elements are connected to the at least one antenna. At least a part of the plurality of receiving elements contributes to time-division multiplexing of receiving the image signal and processing the image signal.