A degree of approach of an object in positions of a detection surface is periodically detected by a sensor unit, a group of detection data items indicating a result of the detection is generated in every one of cycles. The group of detection data items generated in the sensor unit is acquired in every one of cycles by a detection data acquisition unit. In the error determination unit, it is determined in every one of cycles whether there is an error in the detection operation due to noise based on a degree of a temporal change and a degree of a positional change in the detection data. When it is determined by the error determination unit that there is an error in the detection operation of one cycle, a process of acquiring the detection data generated in the one cycle is skipped in the detection data acquisition unit.