A reception cycle control method in which a mobile station and a radio base station control a downlink data reception cycle in the mobile station for downlink data to be transmitted from the radio base station to the mobile station, comprising the steps of: A) starting, at the radio base station, a transmitting-side timer upon transmission of downlink data to the mobile station; B) changing, at the radio base station, a reception cycle of downlink data in the mobile station, when transmitting no downlink data during a period from start to expiration of the transmitting-side timer; C) starting, at the mobile station, a receiving-side timer upon receipt of downlink data transmitted from the radio base station; and D) changing, at the mobile station, a reception cycle of downlink data in the mobile station, when receiving no downlink data during a period from start to expiration of the receiving-side timer; the method being characterized in that: upon transmission of a last piece of downlink data accumulated in a transmission buffer to the mobile station, the radio base station starts both of a Polling timer and the transmitting-side timer, the Polling timer set to expire earlier than the transmitting-side timer and the receiving-side timer; when the Polling timer expires, the radio base station notifies the mobile station of the expiration, and restarts the transmitting-side timer; and the mobile station restarts the receiving-side timer in response to the notification. A) starting, at the radio base station, a transmitting-side timer upon transmission of downlink data to the mobile station; B) changing, at the radio base station, a reception cycle of downlink data in the mobile station, when transmitting no downlink data during a period from start to expiration of the transmitting-side timer; C) starting, at the mobile station, a receiving-side timer upon receipt of downlink data transmitted from the radio base station; and D) changing, at the mobile station, a reception cycle of downlink data in the mobile station, when receiving no downlink data during a period from start to expiration of the receiving-side timer; the method being characterized in that: upon transmission of a last piece of downlink data accumulated in a transmission buffer to the mobile station, the radio base station starts both of a Polling timer and the transmitting-side timer, the Polling timer set to expire earlier than the transmitting-side timer and the receiving-side timer; when the Polling timer expires, the radio base station notifies the mobile station of the expiration, and restarts the transmitting-side timer; and the mobile station restarts the receiving-side timer in response to the notification. upon transmission of a last piece of downlink data accumulated in a transmission buffer to the mobile station, the radio base station starts both of a Polling timer and the transmitting-side timer, the Polling timer set to expire earlier than the transmitting-side timer and the receiving-side timer; when the Polling timer expires, the radio base station notifies the mobile station of the expiration, and restarts the transmitting-side timer; and the mobile station restarts the receiving-side timer in response to the notification.