A battery monitoring circuit for a portable device driven by a secondary battery that supplies an electric current via a wiring pattern formed on a substrate. The battery monitoring circuit includes: a current measuring circuit that measures a current value of a current that flows in the wiring pattern by monitoring an amount of voltage drop that occurs in a specific section of the wiring pattern; a converter that converts the current value into a digital measured current value; a first storage part that stores data for compensating a variation in a resistance value of the wiring pattern depending on an individual particularity of the substrate; and a calculating part configured to correct the digital measured current value by using the data to calculate a corrected current value and to calculate a remaining capacity or to monitor a state of the secondary battery based on the corrected current value.