As a versatile method of detecting and assaying intracellular protein phosphorylation and dephosphorylation that enables nondestructive monitoring as well as spatial and temporal analysis for living cells, animal bodies, plant bodies and the like, a probe for imaging protein phosphorylation and dephosphorylation, which comprises a tandem fusion unit composed of a substrate domain that contains a phosphorylation and dephosphorylation site, a linker sequence and a phosphorylation recognition domain, interposed between a donor chromophore and an acceptor chromophore that cause fluorescence resonance energy transfer, is used.