To provide a portable terminal device capable of preventing a battery from coming off from the portable terminal device even if an external shock is added, for example, by dropping the device, by improving a battery lock device.

The portable terminal device is composed of a portable terminal device main body 2 having a battery housing part 8, batteries 4 housed in the battery housing part, a battery cover 6 arranged at the back face of the portable terminal device main body, and a battery lock device fixing the battery to the portable terminal device main body. The battery lock device is constructed of locking protrusions 32 formed on both side face of the battery housing part of the portable terminal device, engaging ribs 34 protruding from both inner side surface of the battery cover, to be jointed to the locking protrusions in sliding, and coming-off preventing protrusions 36 protruding from both side faces of the battery housing part, preventing the engaging ribs from coming off from the engaging ribs.