To obtain the locking mechanism of a charging device which is capable of locking a battery pack securely when the battery pack of a portable telephone, etc., is charged and, further can clean connection terminals to secure electrical connection.

Pockets 2 and 3 into which battery packs B are inserted are provided in a charger main body 1. Charging terminals 4 are provided on the bottoms of the respective pockets 2 and 3, and protrusions 5 are provided on both the sidewalls of the respective pockets 2 and 3. Grooves 10 are provided in both the side surfaces of the battery pack B, and each groove 10 is composed of a straight groove part 10a and a retaining groove part 10b. The battery pack B is inserted into the pocket to its bottom, while the protrusions 5 are inserted into the straight groove parts 10a of the battery pack B and then the battery pack B is inclined, the battery pack B is securely locked, and furthermore, a connection terminals 11 of the battery pack B are cleaned by the charging terminals 4, so that electrical connection can be established.