The invention provides an interface level meter and an interface level measuring method. The interface level meter is used for measuring the interface level of mixed liquid and comprises a conduit, an ultrasonic wave transceiver and a floater. The ultrasonic wave transceiver is fixedly arranged in the conduit, the floater is located in the conduit, the density of the floater is between the densities of two adjacent layers of media of the to-be-measured mixed liquid, an ultrasonic wave reflecting face is arranged on the side, close to the ultrasonic wave transceiver, of the floater, and the receiving-emitting end of the ultrasonic wave transceiver is towards the floater. According to the interface level meter in the technical scheme, ultrasonic waves emitted by the ultrasonic wave transceiver are returned through the floater located at the interface level position, returned energy is higher, and the position of the interface level can be more accurately reflected; in addition, the wave length of the ultrasonic waves is large, the ultrasonic waves can more easily bypass an interference object and are not prone to being disturbed by impurities in the mixed liquid, a false interface level can be avoided, and interface level measuring accuracy and interface level measuring reliability are improved.