The present invention provides a liposome useful as a vaccine adjuvant. More specifically, the present invention provides a liposome which comprises a lipid bilayer comprising dimyristoylphosphatidylcholine and egg phosphatidylglycerol and a conjugated compound in which a low-molecular weight compound enhancing the physiological activity of TLR7 is bound to squalene via a linker, said conjugated compound being encapsulated in the lipid bilayer.