A metastable state detection device and method, and an ADC circuit are disclosed. The metastable state detection device includes: a delay unit which is configured to receive a synchronization signal and delay the synchronization signal based on preset step delay values; a first flip-flop unit including a first clock input terminal, a first data input terminal and a first data output terminal, wherein the first clock input terminal is configured to receive a clock signal; the first data input terminal is configured to receive the delayed synchronization signal; a second flip-flop unit including a second clock input terminal, a second data input terminal and a second data output terminal; a processing module connected to the second data output terminal, which is configured to receive a target clock signal and detect a metastable state of the first flip-flop unit according to the target clock signal.