Device control method, device management system, and in-home server device connected to device management system

A device control method for a device management system according to the present disclosure receives a device password for using an in-home server device from an information device via an out-of-home network, said device password having been entered into the information device using a setting screen, associates and manages a device ID, a user ID, and the device password, and transmits the device password to the in-home server device so that the in-home server device associates and manages the device ID and the device password. When a login has been authenticated, the device control method transmits an authentication screen to the information device via the out-of-home network, then receives an additional password from the information device via the out-of-home network, said additional password having been entered into the information device using the authentication screen, and if the received additional password is identical to the device password associated with the user ID, permits the information device to operate the target device.