An object of the present invention is to provide a directionality judging method for an operation key in a direction detecting switch, capable of detecting a key operation in any direction; and superior as the cursor can be freely moved by one operation key.The present invention is a directionality judging method for an operation key comprising; wherein an initial value is set whose unit is a minimum division region as a criterion for specifying the operation direction of the operation key from the input signal, and a position of the operation key at a time when it is pressed is detected from the input signal and the operation direction is stored in a memory; and next, an effective operation range comprising the plurality of regions of minimum division regions including the operation direction of the operation key is set in a controller; an operation of the operation key whose state is in the effective operation range is judged to be the same direction; and for an operation at a position at which the operation key deviates from the effective operation range, a new operation direction at the deviating position and an effective operation range are set.