The present invention relates to a novel compound, to a pharmaceutically acceptable salt or optical isomer thereof, to a method for preparing same, and to a pharmaceutical composition for the prevention or treatment of viral diseases containing same as an active ingredient. The novel compound according to the present invention not only has low cytotoxicity but also has excellent antiviral activity against picornavirus such as coxsackievirus, enterovirus, echovirus, poliovirus and rhinovirus, and thus can be effectively used as a pharmaceutical composition for the prevention or treatment of viral diseases such as infantile paralysis, acute hemorrhagic conjunctivitis, viral meningitis, hand-foot-and-mouth disease, vesicular disease, hepatitis A, myitis, myocarditis, pancreatitis, diabetes, epidemic myalgia, encephalitis, cold, herpangina, foot-and-mouth disease, asthma, chronic obstructive pulmonary disease, pneumonia, sinus infection, or otitis media.