Measurements of the spectroscopic characteristics of argon plasma produced by multistage pseudospark discharges are described. Absorptions are observed when a cw argon ion (ArII) probe laser, whose wavelengths are 488.0, 476.5, and 514.5nm, passes through the pseudospark argon plasma. The number densities of the upper laser levels for 488.0, 476.5, 514.5, 351.1, and 363.8nm are (2.9±0.3)×10¹⁵/cm³, (2.4±0.2)×10¹⁵/cm³, (2.4±0.2)×10¹⁵/cm³, (4.1±0.4)×10¹⁴/cm³, (4.0±0.4)×10¹⁴/cm³, respectively at 0.8 Torr of Ar, and at a discharge current density of 3.4 kA/cm². The calculated population inversion density of 488.0nm is-1.4×10¹¹/cm³ (no inversion) under the same operational conditions. This is due to the electron collisional mixing of laser levels and the radiation trap between the lower laser level and the ground ionization level. When the pseudospark argon plasmas are placed in the injection-seeded optical resonators, amplifications of 514.5nm and 476.5nm laser lines are observed.