A secondary-battery chargeable-limit detecting method that detects a charge rate of a chargeable limit and a device of the same are provided. In the chargeable-limit detecting method of the present embodiment, if it is determined that: a temperature measurement value Tm is higher than a temperature threshold Tt in step S3, a voltage measurement value Vm is higher than a voltage threshold Vt in step S4, a voltage excess rate RV is larger than a voltage excess rate threshold Rt in step S11, and an average current Ia is within a predetermined current threshold range in step S12; condition satisfied duration tc in which the conditions of the chargeable limit are satisfied is calculated in step S13. Then, if it is determined that the condition satisfied duration tc is longer than predetermined duration threshold tt in step S15, SOC of the chargeable limit is set in step S16.