Provided is a stable solid preparation comprising 6-((7S)-7-hydroxy-6,7-dihydro-5H-pyrrolo[1,2-c]imidazol-7-yl)-N-methyl-2-naphthamide (orteronel), D-mannitol and an alkaline earth metal salt selected from magnesium aluminometasilicate or calcium silicate. It is preferred that the D-mannitol used is produced by a spray dry production method to provide a downsized preparation. 6-((7S)-7-hydroxy-6,7-dihydro-5H-pyrrolo[1,2-c]imidazol-7-yl)-N-methyl-2-naphthamide is an anti-cancer agent.
