To provide a safe and secure battery device.

This battery device is equipped with an electric circuit 12 and an external electrode 13 which are connected to a battery body 11, and a temperature fuse 14 mounted to the battery body 11 though the electric circuit 12 and the external electrode 13. The temperature fuse 14 has a first insulating film to which a first metal terminal 15 and a second metal terminal 16 are mounted, and a soluble alloy positioned in the upper part of the first insulating film and connected between one end part of the first metal terminal 15 and one end part of the metal terminal 16, the other end part of the first metal terminal 15 is connected to the electric circuit 13, the other end part of the second metal terminal 16 is connected to the external electrode 13, and the thermal conductivity of the first metal terminal 15 is made smaller than the thermal conductivity of the second metal terminal 16.