Human epidermal growth factor receptor 2 (HER2) is highly expressed in breast cancers and is strongly associated with cancer recurrence and prognosis. Nowadays, HER2 antibodies have been used for anticancer drugs. However, because long-term administration of these drugs leads to drug resistance, new therapeutics have been required. Here, we report a bispecific DNA-aptamer-based HER2-targeted lysosome-targeting chimera (HER2-LYTAC) using a HER2-binding DNA aptamer (HER2ap) and an insulin-like growth factor 2 receptor-binding DNA aptamer (IGFIIRap) with a 22 bp linker. The HER2-LYTAC markedly induces HER2 protein degradation, but HER2ap and IGFIIRap do not. The degradation is inhibited by the inhibition of endocytosis and rescued by lysosome inhibitors, suggesting that HER2-LYTAC induces HER2 endocytosis and its degradation within lysosomes. Further, the HER2-LYTAC suppresses HER2-positive cell proliferation via inhibition of HER2-dependent intracellular signaling. The HER2-LYTAC has the potential to be used as a therapeutic agent for HER2-positive cancer.