For system-level understanding of various cellular events, it is vital to identify all molecules participating in each process and understand their interactions in a quantitative manner with spatiotemporal resolution. The advent of recent proteomics approaches has enabled large scale analyses of the quantities and interactions of proteins, the most important biomolecules, in the budding yeast Saccharomyces cerevisiae. In particular, differential protein expression analysis can be achieved by mass spectrometry with stable isotope labeling either in vitro or in vivo to quantify relative difference in protein abundance. Furthermore, researchers are further developing these techniques for absolute quantification of proteins as well as their modifications and interactions, aiming to grasp more precise pictures of the underlying molecular mechanisms for the system-level understanding. Here we review recent advance of quantitative proteomic approaches, focusing on those using mass spectrometry.