The present invention provides double-stranded nucleic acids that suppress the expression of the APCS gene, the double-stranded nucleic acids comprising sense-strand nucleic acids and antisense-strand nucleic acids, and including an at least 11-base-pair duplex strand region； wherein an oligonucleotide strand of at least 17 nucleotides and no more than 30 nucleotides long in the antisense-strand nucleic acids is complementary with a target APCS mRNA sequence including a base sequence represented by any of SEQ ID NOS. 1288–1930.
