The present invention relates to a mode switching method for a multi-mode multiband mobile communication terminal in a multi-access communication network, which is capable of effectively providing handoff to the user mobile communication terminal in heterogeneous communication networks. The method includes the first step of calculating the link quality of a Wireless Local Area Network (WLAN); the second step of comparing the link quality with a first reference value; the third step of measuring a signal from the portable Internet having coverage wider than that of the current communication network if it is determined that the link quality of the WLAN is lower than the first reference value; the fourth step of calculating the link quality of the portable Internet; and the fifth step of switching the mode of the mobile communication terminal to perform handoff to the portable Internet if it is determined that the link quality of the portable Internet is higher than a second reference value.