Battery-state monitoring system

A battery-state monitoring system for precisely and efficiently estimating the state and service life of each of a plurality of storage batteries while suppressing variations in voltage between the batteries in a large-scale power-supply system that is provided with the storage batteries charged with power generated by utilizing natural energy is provided. The system includes a power supply control device that detects a current in each storage battery, an end device that measures temperature, voltage, and internal resistance of each battery, the internal resistance being measured by using at least two or more kinds of frequencies, and a prime monitoring device that acquires measurement data from the end device corresponding to each battery and issues an instruction related to an operation to the power supply control device and the end device. The prime monitoring device estimates degradation of each battery based on one or more of temperature, voltage, internal resistance.