An aminated oligonucleotide probe is provided, in which the amino group possesses improved reactivity. The present invention relates to an oligonucleotide probe, which is represented by general formula 1: ##STR00001## (wherein R.sub.1 is a hydrogen atom or a protecting group for an amino group, R.sub.2 and R.sub.3 are each independently a divalent organic group, and A is an oligonucleotide).