A sensor of pyrophosphate which can detect pyrophosphate conveniently with high sensitivity in a method for measuring pyrophosphate in SNP typing utilizing a primer extension reaction is provided.A sensor of pyrophosphate which is characterized by including: an insulative substrate 1; an electrode system that is formed thereon and has a measurement electrode 2 and a counter electrode 3; and a plurality of reaction reagent layers that are provided on the substrate 1 and include pyrophosphatase, glyceraldehyde-3-phosphate dehydrogenase, diaphorase, glyceraldehyde-3-phosphate, oxidized nicotineamide adenine dinucleotide, an electronic mediator, a magnesium salt and a buffer component, reaction reagent layer 36 including the enzyme being separated from reaction reagent layer 35 including the buffer component, and reaction reagent layer 37 including glyceraldehyde-3-phosphate being separated from the reaction reagent layer 35 including the buffer component.