To provide a secondary battery device that is mounted to electronic equipment as its electric source and can considerably reduce an inner consumption power in separated state with a simple structure.

The secondary battery device comprises a battery body 1 and control circuit 10 being operated by electric power supplied from the battery body. The secondary battery device further comprises a switch 15 (electric field effect transistor) for interrupting the electric power supplied from the battery body to the control circuit, a buffer circuit 16 (mount detecting means) for detecting the state of the secondary battery device to the electronics, and a drive circuit 17 (consumer power suppressing means) for switching the switch when the secondary battery device is not mounted to the electronics. Therefore, the inner consumption power can be reduced, as the switch is switched off when the secondary battery device is not mounted to the electronics.