There is provided a radio interrogator system which reduces the interference with a radio transponder and avoids the decrease in throughput of the entire system in a case in which a plurality of radio interrogators are disposed at positions brought relatively close to each other and are simultaneously placed into operation. The plurality of radio interrogators are classified into two groups and each of the radio interrogators has an operation mode setting unit capable of exclusively setting, for each of the classified groups, a transmission mode for transmitting a radio transmission signal to a radio transponder or a reception mode for receiving a radio response signal transmitted from the radio transponder as a response to a radio transmission signal from the radio interrogator.