Introduction: Epidermal growth factor receptor (EGFR) overexpression, which is observed in 27-44% of gastric cancer (GC) patients, has been generally reported to be a poor prognostic factor. Serum soluble heparin-binding EGF-like growth factor (sHB-EGF) level was reported elevated in patients with more advanced gastric cancer. GC1118 is a novel EGFR antibody with a pronounced inhibitory activity on high-affinity EGFR ligand-induced EGFR signaling. In this study, we evaluated the therapeutic potential of GC1118 in gastric cancer by determining EGFR ligand-induced proliferation, migration and invasion of gastric cancer cells. Methods: EGFR ligand expression levels in serum and tissues of gastric cancer patients were determined by ELISA and immunohistochemistry. The inhibitory efficacy of GC1118 on ligand-induced migration and invasion was evaluated using trans-well culture plate. Results: Serum levels of EGFR ligands including sHB-EGF were determined from 100 patients with gastric cancer and 40 healthy donors. sHB-EGF and amphiregulin (AREG) were significantly higher in patients with gastric cancer than in healthy donors. Unlike other reports, however, we did not observe any correlative increase of those ligands with disease stage. HB-EGF was highly expressed in gastric cancer tissues than non-cancer tissues but did not reach statistically significance. While GC1118 inhibited a broad range of EGFR ligand-induced EGFR signaling and proliferation, inhibitory activity of cetuximab was restricted to AREG. Moreover, GC1118 showed superior inhibitory activity on high-affinity ligand-induced migration and invasion compared with cetuximab and panitumumab. Pronounced inhibition on signaling molecules related to migration such as EGFR pY845, p130cas pY416, and FAK pY925 was also observed with GC1118. Conclusion: Compared with other EGFR antibodies, GC1118 exhibited more profound suppressive activity on HB-EGF-induced EGFR signaling, migration, and invasion of gastric cancer cells. Our study suggests that GC1118 might have therapeutic advantage in the treatment of metastatic gastric cancer patients with a high level of HB-EGF.