Device for detecting cracks of concrete member through ultrasonic method

A device for detecting concrete member cracks through an ultrasonic method comprises a main ruler and an ultrasonic transducer, scale marks are marked on one side of the main ruler, a first marking part is arranged at one end of the main ruler, a first marking groove is formed in the first marking part, and a sliding piece is arranged on the main ruler in a sliding mode; the sliding piece comprises a sliding block arranged on the main ruler in a sliding mode, an upper extending plate arranged on the sliding block and a lower extending plate arranged on the sliding block, the lower extending plate is provided with a reading line, the sliding piece is provided with a second marking part, a second marking groove is formed in the second marking part, and the ultrasonic transducer comprises a first transducer and a second transducer. The first transducer and the second transducer are arranged on the corresponding first marking groove and the second marking groove respectively, and a fixing assembly used for fixing