A peripheral connected to a host computer is prevented from unexpectedly coming to be in a non-connection state due to control of the host computer. Further, even when the peripheral such as an electronic camera cannot enough receive power necessary for the device itself from a connection line such as a USB, the peripheral is made to be able to use the power effectively. To achieve this, there is disclosed a computer peripheral which is connected to the host computer and comprises a connection signal transmitter for transmitting to the host computer a signal to control the connection with the host computer and a controller for shifting an operation state of the computer peripheral to a low consumption current mode after notifying a user and obtaining approval of the user before transmitting a signal to control into the disconnection state to the host computer by the connection signal transmitter.