A synchronous rectification device is adapted to control a conversion circuit, where he conversion circuit includes: a primary side coil, configured to receive input power; and a secondary side coil, configured to generate inductive power in response to the input power. The synchronous rectification device includes: a first control circuit, configured to provide a first control signal to control the primary side coil; a secondary side switch, configured to generate an ON signal and an OFF signal according to the inductive power; an isolation coupling element; and a second control circuit. The isolation coupling element includes: a receiving side, configured to receive the first control signal; and a reaction side, configured to generate a coupling signal in response to the first control signal. The second control circuit outputs a second control signal according to the coupling signal, the ON signal, and the OFF signal to adjust the inductive power.