A data backup method according to the present invention includes steps of: when a first account is logged in, obtaining information of a SIM card; registering a second account when determining that the SIM card of a terminal is changed from a first SIM card to a second SIM card; executing a predetermined data backup process so as to back up data corresponding to the first account to the second account; and sending a deletion instruction to a server for instructing the server to delete the data corresponding to the first account.