A medicinal composition for preventing or treating secondary hyperparathyroidism under maintenance dialysis, said medicinal composition comprising 3-{[(2S)-2-amino-2-carboxyethyl]carmaboylamino}-5-chloro-4-methylbenzenesulfonic acid or a pharmaceutically acceptable salt thereof, or a solvate of the same which is to be administered by a predefined route in a predefined dosage. According to the present invention, it is possible to provide a prophylactic or therapeutic agent for secondary hyperparathyroidism under maintenance dialysis, said agent showing reduced side effects or no significant accumulation. This medicinal agent allows easy administration management and has a high safety compared with conventional products.