A paging signal transmitting method includes a step of allowing each of mobile stations (UE) to receive security data from a network node (1) via a channel specified by a paging signal, a step of allowing each mobile station (UE) to calculate a third set of security information by using an open first set of security information and a second set of security information managed by each mobile station, a step of allowing each mobile station (UE) to compare the third set of security information with a fourth set of security information included in the received security data to verify the validity of the paging signal, and a step of allowing each mobile station (UE) to output a signal corresponding to the paging signal when the validity of the paging signal is verified.