The present invention provides a nucleic acid complex represented by formula 1, the nucleic acid complex being capable of suppressing the expression of [beta]2GPI. Formula 1: (in formula 1, X is a double-stranded nucleic acid that comprises a sense strand and an antisense strand and includes a duplex region of at least 11 base pairs； the double-stranded nucleic acid is complementary with any of the [beta]2GPI mRNA sequences of interest described in Tables 1-1 to 1-16 in an oligonucleotide strand having a strand length of 17-30 nucleotides in the antisense strand, and the 3' end or 5' end of the sense strand binds to S3； L1 and L2 each independently a sugar ligand； and S1, S2, and S3 each independently represent a linker).本發明提供一種下述式1所表示之能夠抑制β2GPI之表現之核酸複合體。 式1： [化1](式1中， X為包含正義股及反義股且包含至少11個鹼基對之雙鏈區域之雙股核酸， 該雙股核酸於該反義股中之鏈長為17個～30個核苷酸之寡核苷酸鏈與表1-1～表1-16中所記載之靶β2GPI mRNA序列之任一者互補， 該正義股之3'末端或5'末端鍵結於S3， L1及L2分別獨立為糖配體， S1、S2及S3分別獨立為連接子)
