Imaging mass spectrometry (IMS) is a two-dimensional mass spectrometry to visualize the spatial distribution of biomolecules that does not need either separation or purification of target molecules and enables us to monitor not only the identification of unknown molecules but also the localization of numerous molecules simultaneously. Among the ionization techniques, matrix-assisted laser desorption/ionization (MALDI) is one of those most generally used for IMS, which allows the analysis of numerous biomolecules ranging over wide molecular weights. At present, targets of IMS research have expanded to the imaging of small endogenous metabolites such as lipids, exogenous drug pharmacokinetics, exploring new disease markers, and other new scientific fields.