A steam trap monitoring system includes: a steam trap; an opening/closing valve for opening/closing a channel to the steam trap, the opening/closing valve being located on upstream side of the steam trap; a sensor for detecting one or more physical quantities; and an analysis unit for analyzing detection information from the sensor. In this steam trap monitoring system, the analysis unit is configured to analyze both a functional state of the steam trap and a functional state of the opening/closing valve, based on detection information from the single sensor.