A battery remaining capacity detection method calculates a remaining capacity of a battery having the possibility that a memory effect occurs by using correlation between an voltage V.sub.0 and the remaining capacity. Correlation between a reset voltage V.sub.o reset that is obtained by subtracting a value obtained by multiplying an occurrence amount V.sub.m based on the memory effect by a memory effect occurrence amount correction value C(SOC) from an initial voltage V.sub.o ini and the remaining capacity is obtained, in the battery after use, based on correlation between the initial voltage V.sub.o ini and the remaining capacity. The remaining capacity is obtained by setting the voltage V.sub.0 of the battery after use as the reset voltage V.sub.0 reset. This method provides precise battery detection without completely discharging.