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Herein a non-contact non-destructive method to generate Lamb waves against a target structure is proposed using an impulse excitation force generated by laser-induced plasma (LIP). Conventional methods to generate Lamb waves include using a contact-type device such as piezoelectric zirconate titanate and a non-contact device such as an air-coupled transducer or laser thermoelasticity. Previously, we produced Lamb waves against a target structure using a non-contact excitation force generated by laser ablation (LA). By monitoring the propagation of Lamb waves, we successfully detected artificially penetrated cracks in the target structure. Lamb wave generation method by LA can be used for a curved surface or an underwater structure that is difficult to be applied with a contact-type device. Compared to a non-contact device, the generated Lamb waves have higher amplitudes, improving the signal-to-noise ratio, which consequently reduces the number of averaging and benefitting from decreased measurement time , but damages the irradiated part on the sub-millimeter length scale. LIP irradiates a high-power pulse laser in air, forming a plasma when its laser fluence exceeds 10^15 [W/m^2]. The plasma in air rapidly expands, generating shock waves on a spherical surface. These shock waves become the excitation force against a target structure. In this experiment, an aluminum alloy 2024 plate is used as a test piece, and the phase velocity and the group velocity of the generated Lamb waves are compared to the calculated values from the Rayleigh–Lamb frequency equations. The maximum error is 5% and its frequency component includes at least 400 kHz.