Provided is an anti-claudin-1 monoclonal antibody that exhibits sufficient inhibitory activity against HCV infection. The antibody is a mouse anti-claudin-1 monoclonal antibody. The antibody is also an anti-claudin-1 monoclonal antibody that recognizes an epitope in the second extracellular loop of human claudin-1 and binds to human claudin-1. Also provided is an anti-HCV therapeutic agent comprising, as active components thereof, an anti-claudin-1 monoclonal antibody, a mouse anti-claudin-1 monoclonal antibody, a human chimeric anti-claudin-1 monoclonal antibody, and a humanized anti-claudin-1 monoclonal antibody.