FIP vaccines were provided that use an N protein with a specific structure, or a fragment thereof, as an antigen. Preferred antigens of this invention are N proteins derived from a specific type I virus strain (KU-2). Vaccines comprising such an N protein confer preventive effects against a wide range of FIPVs. In addition, the N proteins are very safe because they do not comprise epitopes that enhance infection. Furthermore, preventive effects can be accomplished against type I viruses, which actually cause 70% or more of FIP.