1. A judgment apparatus comprising: a storage configured to store first reference data representing data that a detector should output in a first area when a detection target passed the first area, and second reference data representing data that the detector should output in the first area when the detection target passed a second area being different from the first area; and a processor to perform processes of: obtaining data from the detector outputting, in a time-series manner, data according to a detection condition of the detection target passing the first area or the second area; judging a degree of similarity between data obtained by the obtaining and the first and second reference data stored in the storage; and judging whether or not the detection target passed the first area, based on the judgment result by the judging the degree of similarity.