PURPOSE: To provide an apparatus and a method for charging a constant amount without being affected by the change in ambient temperature during the charging of a secondary battery.

CONSTITUTION: A timer circuit 10 has a function of an operation for a constant time by a signal from a battery connection detecting part 9, and a control part 11 has a function of an operation by a signal of the timer circuit 10 and subsequently a feeding of the signal to a charging circuit 12 and an arithmetic circuit 16. The charging circuit 12 charges a nickel-hydrogen battery 8, and the arithmetic circuit 16 calculates on the basis of measuring results of the nickel-hydrogen battery R and an atmospheric temperature by temperature sensors 14a and 14b, and when the calculated value reaches a predetermined value, the signal is fed to the control part 11 and the charging of the nickel- hydrogen battery 8 is terminated.