Protein phosphorylation is a reversible post-translational modification crucial in signal transduction. To understand signaling processes, it is important to identify phosphorylated proteins and their phosphorylation sites. Because phosphorylation is a dynamic process, elucidation of signaling networks also requires quantitation of these phosphorylation events. This report summarizes recent advances in techniques for phospho-proteomics by using mass spectrometry. In this review, we offer an overview of the several technologies to elucidate phosphoproteome currently available. These technologies involve the enrichment of phosphorylated proteins/peptides and identification and quantification by mass spectrometry.