A mobile communication method, comprising: a step in which a mobile communication apparatus moves from a pre-movement source access router apparatus to a movement-destination access router apparatus and determines whether the pre-movement source access router apparatus connected therewith complies with Fast Mobile IP or not; a step in which the mobile communication apparatus during its movement detects a signal from the movement-destination access router apparatus; and a step in which, in the case where the mobile communication apparatus has determined that the pre-movement source access router apparatus does not comply with Fast Mobile IP, when detecting the signal, the mobile communication apparatus sends a router solicitation for proxy including a lower layer address of the movement-destination access router apparatus to the home agent apparatus through the pre-movement source access router, the home agent apparatus after receiving the router solicitation for proxy (see page 58 lines 1-4) searches an access router information list for information on the movement-destination access router apparatus based on the lower layer address of the movement-destination access router apparatus, and if the home agent apparatus determines that the movement-destination access router apparatus complies with Fast Mobile IP, the home agent apparatus sends a proxy router advertisement in whose new router prefix field is written the IP address obtained from information on the access router apparatus which corresponds to the lower layer address, the mobile communication apparatus receives the proxy router advertisement message through the pre-movement source access router and acquires the IP address written in the new router prefix field as information on the movement destination access router apparatus, and the mobile communication apparatus sends a fast binding update message to the home agent apparatus through the pre movement source access router wherein the IP address included in the information on the movement destination access router is written in the replacement care-of address field, the home agent apparatus, after receiving the fast binding update message, transmits the handover initiate message to the IP address of the movement destination access router indicated in the replacement care-off address field of the fast binding update message wherein the U-flag for instructing the movement destination access router to buffer packets is set, the home agent apparatus receives packets addressed to the home address of the mobile communication apparatus and forwards them to the movement destination access router. a step in which a mobile communication apparatus moves from a pre-movement source access router apparatus to a movement-destination access router apparatus and determines whether the pre-movement source access router apparatus connected therewith complies with Fast Mobile IP or not; a step in which the mobile communication apparatus during its movement detects a signal from the movement-destination access router apparatus; and a step in which, in the case where the mobile communication apparatus has determined that the pre-movement source access router apparatus does not comply with Fast Mobile IP, when detecting the signal, the mobile communication apparatus sends a router solicitation for proxy including a lower layer address of the movement-destination access router apparatus to the home agent apparatus through the pre-movement source access router, the home agent apparatus after receiving the router solicitation for proxy (see page 58 lines 1-4) searches an access router information list for information on the movement-destination access router apparatus based on the lower layer address of the movement-destination access router apparatus, and if the home agent apparatus determines that the movement-destination access router apparatus complies with Fast Mobile IP, the home agent apparatus sends a proxy router advertisement in whose new router prefix field is written the IP address obtained from information on the access router apparatus which corresponds to the lower layer address, the mobile communication apparatus receives the proxy router advertisement message through the pre-movement source access router and acquires the IP address written in the new router prefix field as information on the movement destination access router apparatus, and the mobile communication apparatus sends a fast binding update message to the home agent apparatus through the pre movement source access router wherein the IP address included in the information on the movement destination access router is written in the replacement care-of address field, the home agent apparatus, after receiving the fast binding update message, transmits the handover initiate message to the IP address of the movement destination access router indicated in the replacement care-off address field of the fast binding update message wherein the U-flag for instructing the movement destination access router to buffer packets is set, the home agent apparatus receives packets addressed to the home address of the mobile communication apparatus and forwards them to the movement destination access router.