A connecting structure received in a main device for connecting an auxiliary apparatus. The connecting structure includes a retracting part formed on a bottom board of the main device and close to a sidewall of the main device and a clamping part. The clamping part is pivotablly mounted on the bottom board and pivotally connected to the retracting part. The retracting part drives the clamping part to extend out of the main device via an opening defined on the sidewall for connecting the auxiliary apparatus when the auxiliary apparatus needs to be mounted on the main device. The retracting part retracts the clamping part into the main device when the auxiliary apparatus is unmounted from the main device.