A high performance liquid chromatography-electrospray tandem mass spectrometry (HPLC-ESI-MS/$MS^n$) based chemical profiling method was developed to evaluate repetitious steaming-induced chemical transformations in black ginseng (BG and Korean white ginseng subjected to nine cycles of steam treatment). Under the optimized HPLC and ESI-MS/$MS^n$ conditions, more than 13 and 17 peaks were separated and detected in white ginseng (WG) and BG within 85 min, respectively. The components were identified by comparing the mass spectrum and/or matching the empirical molecular formula with that of known published compounds. In total, 17 major ginsenosides were identified in BG, 16 of which were determined to be newly generated during the BG preparatory process. The mechanisms involved were further deduced to be hydrolysis, dehydration, isomerization, and decarboxylation reactions of the original ginsenosides in WG by analyzing nine mimic cycles of steaming extracts of seven pure reference ginsenosides. A significant difference in chemical profiles between BGs developed from two batches of WG suggested that storage duration significantly influenced the quality consistency of not only the crude drug but also the BG derived from WG.