The present invention provides a double-stranded nucleic acid consisting of a sense-strand nucleic acid and an antisense-strand nucleic acid and comprising a double-strand region having at least 11 base pairs, for suppressing expression of APCS gene, in which an oligonucleotide chain having a chain length of at least 17 nucleotides and at most 30 nucleotides in the antisense-strand nucleic acid is complementary to a target APCS mRNA sequence comprising a base sequence set forth in any one of SEQ ID NOS: 1288 to 1930.
