Disclosed is a novel means which enables satisfactory preservation of embryos and fertilized eggs in the non-frozen state for a longer period than conventional means, which novel means also achieves high hatching ability and a high conception rate of the embryos after the preservation. The method for preserving a mammalian embryo(s) or fertilized egg(s) of the present invention comprises immersing a mammalian embryo(s) or fertilized egg(s) in a medium containing 20 to 80% (v/v) serum and 10 to 100 mM Good's buffer, and storing the embryo(s) or fertilized egg(s) at non-freezing low temperature. The preservative solution for a mammalian embryo(s) or fertilized egg(s) of the present invention essentially consists of a medium containing 20 to 80% (v/v) serum and 10 to 100 mM Good's buffer. The Good's buffer is preferably HEPES.
