An MS 300 controls a mobility level (IMM) of user device in an idle mode depending on a movement; state of the user device. The ME 300 includes a movement state acquisition section 320 that acquires the movement state of the user device, a mobility level selector 330 chat selects a mobility level out of the multiple mobility levels based on the movement state of the user device acquired by the movement state acquisition section 320, and a mobility level notification section 340 that notifies the user device of the mobility level selected by the mobility level selector 330.