To make a correct decision for being-in-range cell with improvement of scanning order for perch channels of peripheral cell in a mobile station device deciding the being-in-range cell by the perch channels.

A perch channel scanning part 1-41 scans the perch channels of the peripheral cell in order of low receiving level of the last receiving stored in a storing circuit 1-9. An electric field measuring circuit 1-3 measures a receiving level of the perch channel received sequentially by the perch channel scanning so as to store the measured level into the storing circuit 1-9. After scanning for all perch channels of the peripheral cell, the stored receiving level is compared at a receiving level comparing part 1-51, so that the cell of the perch channel of the highest receiving level is decided as the being-in-range cell.