PROBLEM TO BE SOLVED: To provide a multi-nucleic reaction tool capable of subjecting a plurality of different target sequences to an amplification reaction simultaneously and independently using a plurality of different primer sets in one reaction field, and independently determining a presence/absence or the amount of the target sequences for each of amplified products of the primer sets, and to provide a method for detecting a target nucleic acid using the same.SOLUTION: A multi-nucleic acid reaction tool of an embodiment is equipped with a support, a plurality of different primer sets, and probe nucleic acids comprising a complementary sequence of a target sequence. The support is configured to support a liquid-phase reaction field. On at least one surface of the support which is in contact with the reaction field when the reaction field is formed using the liquid phase, the plurality of different primer sets are fixed in a releasable manner to mutually independent primer immobilization regions for each ty
