A nucleic acid probe represented by formula (Ia) ##STR51## wherein, M is an alkyl group substituted with a primary amine group which allows an attachment of a marker X, which is detectable in a non-isotopic manner by production of color or light,
- L is an alkyl group,
- S is an ofigonucleotide,
- J is H or OH;
- B is a purine or pyriraidine, and m is an integer of from 1 to 1000;
- x and x' are each 0 or an integer of from 1 to 100, and
- n' is 0 or an integer of from 1 to 20;
- y and y' are each an integer of from 1 to 100, and
- n is an integer of from 2 to 20;
- wherein said X is selected from the group consisting of fluorescein, any enzyme capable of producing a color or a light in the presence of a substrate, a hapten, and a protecting group of the primary amine group and said LM is introduced at the 5'(OH) where z'.noteq.0 and z=0,
- at the 3'(OH) where z'=0 and z.noteq.0,
- simultaneously at the 5'(OH) and at the 3'(OH)
- where z'.noteq.0 and z.noteq.0,
- z and z' are individually each 0 or an integer of from 1 to 100,
- with the proviso that z and z' are not simultaneously 0.