A prophylactic, ameliorating or therapeutic agent for a retinal disease, the agent comprising geranylgeranylacetone which (a) is a mixture of (5E,9E,13E)-geranylgeranylacetone and (5Z,9E,13E)-geranylgeranylacetone, the (5E,9E,13E)-geranylgeranylacetone content of the mixture being 80% by weight or more, (b) consists of (5E,9E,13E)-geranylgeranylacetone, or (c) consists of (5Z,9E,13E)-geranylgeranylacetone directly suppresses the death of a retinal cell, thereby fundamentally preventing, ameliorating or treating the retinal disease.