The present invention relates to an automatic tourniquet that is easy to carry and store, and is capable of applying an appropriate pressure. A first body with a built-in bobbin rotating by a driving motor and having a first opening on one side, and a second opening on one side are formed. And a second body that is detachable from the first body, one end is fixedly coupled to the bobbin, part is wound around the bobbin, and the other end is fixedly coupled to the second body through the first opening and the second opening. A band, a fastening sensing unit that detects whether the first body and the second body are coupled, a band sensing unit that detects the amount of winding or unwinding of the band from the bobbin, and applied to the bleeding or blood collection target site by the band And a pressure sensing unit that senses a losing pressure, and a control unit that receives a signal sensed from at least one of the fastening sensing unit, the band sensing unit, and the pressure sensing unit, and controls the driving motor through the received signal.