The present invention relates to novel 6-methylnicotinamide derivatives and their pharmaceutically acceptable salts, the process for preparing them, and the pharmaceutical compositions containing said compounds as active ingredients. The 6-methylnicotinamide derivatives of the present invention exhibit their inhibitory activity against the proliferation of human immunodeficiency virus (HIV) as well as hepatitis B virus (HBV) and hepatitis C virus (HCV), such that they can be used for hepatitis B, hepatitis C and acquired immune deficiency syndrome (AIDS).