Provided is a system for detecting foreign matter in a parison (11) that is discharged successively from a discharge device (21), the system comprising the following: infrared cameras (2) that detectinfrared beams emitted from the parison (11); and a determination unit that determines whether foreign matter is present in the parison (11) on the basis of the infrared beams detected by the infraredcameras (2). A determination area is set in the parison (11) in a discharge direction of the parison (11), a storage unit is provided that stores an infrared threshold set for the determination area,and the determination unit compares the detected values from the infrared cameras with the threshold.