Disclosed is a method for handling inter-RAT cell measurement in a dual-mode UE in a connected mode, which supports both GSM/GPRS (Global System for Mobile communication/General Packet Radio Service) RAT (Radio Access Technology) and UMTS (Universal Mobile Telecommunications System) RAT. A UTRAN (UMTS Terrestrial Radio Access Network) of the UMTS RAT transmits a measurement control message to a URRC (UMTS Radio Resource Control) of a UMTS network layer in the UE. Upon receiving the measurement control message, the URRC sends a measurement request for GSM cells to an RR/GRR (Radio Resource/GPRS Radio Resource) of a GSM/GPRS network layer. The RR/GRR activates a GSM physical layer and sends a measurement request for the GSM cells to the GSM physical layer. The GSM physical layer performs measurement on the GSM cells and reports a measurement value to the RR/GRR. The RR/GRR reports the measurement value for GSM cells, received from the GSM physical layer, to the URRC. The URRC reports the received measurement value for GSM cells to the UTRAN.