In this study Lamb waves propagating in a laminated composite plate with stepped thickness variance are characterized through experiments. Understanding the characteristics of Lamb waves is very important for developing a structural health monitoring system, as the number, size, and location of transducers should be determined at the structural design stage. Thin piezoelectric (PZT) transducers bonded to the surface were used for the generation and reception of Lamb waves. The influences of stepped thickness variance were investigated with measurement of group velocities and frequency analyses of the received signals. In addition, a mode analysis was conducted by a mutual transmitting-receiving method making use of the difference between the signals received from a pair of PZTs consisting of transmitter and receiver.