A dual purpose mini-charger includes: a main charging body having a USB-plug at the front end thereof, the USB-plug being connected to a USB-socket for obtaining the direct current for the charging purpose; two charging grooves adapted to accommodate batteries, the left and right charging grooves being disposed at both sides of the main charging body in an axial direction with respect to the USB-plug; and a charging control circuit board having a front portion adapted to fix a plurality of connecting pins in place such that an electric connection is created, the charging control circuit board further having a rear portion to which two pieces of first terminals are electrically coupled, the first terminals each having a contact piece fitted to an indentation at the bottom end of the left and right charging grooves, a second terminal with the telescopic and conducting function being disposed at an end opposite to the first terminals, the external end projecting at the front end of the charging groove. In this way, a secondary battery charger is small and suitable for charging two types of secondary batteries.