In this study, a simple and effective method for determining whitening agents and parabens, using on-line focusing with sweeping-micellar electrokinetic chromatography (MEKC), was developed. The optimum conditions for the on-line concentration and separation of arbutin, kojic acid, resorcinol, salicylic acid, and methyl-, ethyl-, propyl-, and butyl-parabens were investigated in detail. Sweeping-MEKC was performed at 15 kV using a background electrolyte containing 15 mM tetraborate buffer (pH 8.5), 40 mM sodium dodecyl sulfate, and 0.100% (w/v) poly(ethylene oxide). The analyte detection limits (S/N = 3) were 8–162 nM (1.1–21.0 ng mL⁻¹), and these were 46–279 times lower than those achieved using conventional sample injections (10 s, no polymer in the buffer solution). Baseline separation of all of the analytes was achieved within 10 min. The method was validated and then used to determine whitening agents and parabens in five commercial cosmetic products. The average recoveries from the commercial products were 85.2–118.0%. The proposed method is a powerful alternative approach for identifying and determining whitening agents and parabens in commercial cosmetic samples.