To provide a state detection system and a state detection device capable of detecting approach, repose and separation between the first moving body and the second moving body moving relatively, surely regardless of the attitude, the position relation and a surrounding environment of a transmission/reception device.

This state detection system for detecting at least one state between approach, repose and separation between the first moving body and the second moving body moving relatively, is equipped with the first radio wave communication means 1 provided on the first moving body, for transmitting a required radio wave; the second radio wave communication means 2 provided on the second moving body, for receiving the transmitted radio wave from the first radio wave communication means; a radio wave intensity storage means for detecting and storing in time series the intensity of the radio wave received by the second radio wave communication means; and a state determination means for determining at least one state between approach, repose and separation between the first moving body and the second moving body by comparing the radio wave intensity stored in the radio wave intensity storage means, in time series in a plurality of times.