An apparatus for detecting the state of a storage device prevents occurrence of a leakage current. A low-level detection unit is provided for each of blocks of a battery pack. Control units are connected to the blocks of the battery pack by way of first switches and are started upon receipt of power supply. The control units and measurement units are connected to the blocks by way of second switches. The control units activate the second switches after being started as a result of activation of the first switches, to thus receive power supply, and commence measurement of block voltages by means of the measurement units. The high-level detection unit supplies a read signal and a synchronous signal to the low-level detection units by way of the first switches.