A cell search control that can save power consumption at a mobile device and perform an appropriate in-service area determination is provided. The mobile device according to the present invention includes: a cell search execution unit (120) for detecting a synchronization channel from a base station to perform cell search; a signal reception determination unit (130) for comparing a measurement X of the signal from the base station with a system information reception threshold A and determining whether or not to receive a system information from the base station; and an in-service area determination unit (170) for comparing the measurement X with a minimum required quality level B contained in the system information and determining whether or not to enter into an in-service area state with the base station. Depending on the result of the in-service area determination unit, the reception threshold A or a waiting time for the cell search may be adjusted, or the base station may be excluded from the cell search. Thus, the power consumption at the mobile device can be saved, and an appropriate in-service area determination can be made even when the minimum required quality level B has been changed.