A remote operation system comprising a first mobile communication apparatus, a second mobile communication apparatus, and a relay apparatus, wherein the first mobile communication apparatus comprises transmission means for transmitting a remote operation request, the second mobile communication apparatus comprises: server means; communication means; extraction means for extracting a control message related to control of the server means from messages received by the communication means; and control means for controlling the server means based on the control message, and the relay apparatus comprises: reception means for receiving the remote operation request from the first mobile communication apparatus; storage means for associating first identification information related to a controlled-side communication apparatus or a controlled-side user that is remotely operated with second identification information related to a control-side communication apparatus or a control-side user that remotely operates the controlled-side communication apparatus to store the first identification information in association with the second identification information as permission information; determination means for comparing the first identification information and the second identification information included in the permission information with the first identification information and the second identification information included in the remote operation request, respectively, to determine whether to allow the first mobile communication apparatus to remotely operate the second mobile communication apparatus; and transmission means for generating the control message to transmit to the second mobile communication apparatus the control message upon determination in the determination means that the remote operation is allowed; wherein the control message can be received by the communication means, included in the second mobile communication apparatus, which is constantly operated regardless of whether the server means is operated; the system being characterised in that the control means are adapted for controlling start of the server means when the control message regarding start of the server means is extracted; wherein the transmission means included in the relay apparatus is adapted to transmit the control message using any one of e-mail, SMS, and MMS, and the extraction means included in the second mobile communication apparatus is adapted to extract, from e-mail, SMS, or MMS received by the communication means, e-mail, SMS, or MMS including the control message to output the extracted one to the control means. server means; communication means; extraction means for extracting a control message related to control of the server means from messages received by the communication means; and control means for controlling the server means based on the control message, and reception means for receiving the remote operation request from the first mobile communication apparatus; storage means for associating first identification information related to a controlled-side communication apparatus or a controlled-side user that is remotely operated with second identification information related to a control-side communication apparatus or a control-side user that remotely operates the controlled-side communication apparatus to store the first identification information in association with the second identification information as permission information; determination means for comparing the first identification information and the second identification information included in the permission information with the first identification information and the second identification information included in the remote operation request, respectively, to determine whether to allow the first mobile communication apparatus to remotely operate the second mobile communication apparatus; and transmission means for generating the control message to transmit to the second mobile communication apparatus the control message upon determination in the determination means that the remote operation is allowed;