The present disclosure provides a battery box including a main body and a battery mounting mechanism. The main body defines a battery cavity to receive a battery and includes a sidewall defining a first receiving space and a second receiving space. The mechanism includes a fixing member, a shaft, and an elastic member. Two ends of the shaft are fixed in the first receiving space, and the end adjacent to the second receiving space is nearer to the battery cavity than the other end. The fixing member rotates relative to the shaft and adjacent to the second receiving space. A portion of the fixing member is received in the battery cavity. The elastic member is perpendicularly received in the second receiving space and can be compressed due to the rotation of the fixing member. An electronic device using the battery box is also provided.