Selection of paging group number in mobile communication system and paging method using the same

A device for determining the number of paging groups in a mobile communication system, a method therefor, and a paging method using the method are provided to determine the paging groups in order to reduce an error during a paging indication procedure as decreasing battery consumption of a terminal in the mobile communication system where paging indication is performed through the paging groups. When a base station receives an information delivery indication message including number information of an idle- state terminal from a paging server, the number information of the terminal is stored. The base station calculates the number of paging indicators by using the stored idle-state terminal number information, active-state terminal number information, paging group reflecting coefficients, maximum number information of the idle-state terminal, and maximum number information of an active-state terminal. The calculated paging indicator number information is included in a system information message, and the message is transmitted to the terminal.