A two-dimensionally imaging spectrometer system was employed to measure spatial variations in the intensities of emission lines in a Cu-Mn-Ni alloy sample when they were excited from a laser-induced plasma with krypton gas. The emission zone of these lines shrank and had greater emission intensities with increasing gas pressure, and the intensities of their background also became more intense. It was thus found that the optimum observation zone for the analytical application varied with the pressure of the plasma gas. The two-dimensional distribution of the signal-to-background ratio for each analytical line was investigated to determine the measuring conditions for the emission analysis, indicating that the spatially-resolved measurement was generally superior to the conventional spatially-integrated measurement over the plasma region.