The invention discloses a plate waveform scanning device for a plate heat exchanger, which is composed of a measurement gantry bracket, a plate fixing mechanism, a ball screw linear walking mechanism, a biaxial servo synchronization system, laser scanning sensors and an Advantech ARK-3440 computer measurement and control system, wherein each laser scanning sensor is installed on a sliding block of the ball screw linear walking mechanism, so that the two laser scanning sensor at both sides of a plate are controlled by the servo system so as to move synchronously, thereby being capable of measuring parameters such as the waveform, the plate thickness and the like at the obverse side and the reverse side of the plate at any positions. The plate waveform scanning device disclosed by the invention is convenient and quick in test, high in detection work efficiency and high in measurement precision, improves the work efficiency of quality detection, strengthens inspection means, and is particularly obvious in efficiency improving for large plates. In addition, the plate waveform scanning device solves a problem of thickness reduction which cannot be directly measured before.