A bag abnormality detection device for detecting an abnormality of a bag that is transferred, the bag abnormality detection device comprising: a synchronous sensor that detects presence or absence of the bag at a first detection point in a transfer path of the bag; a first bag detection sensor that detects presence or absence of the bag at a second detection point in the transfer path, the second detection point being at a same position as the first detection point or on an upstream side of the first detection point in regard to a transfer direction of the bag; a second bag detection sensor that detects presence or absence of the bag at a third detection point in the transfer path, the third detection point being at a same position as the first detection point or on a downstream side of the first detection point in regard to the transfer direction of the bag; and a controller that controls the synchronous sensor, the first bag detection sensor and the second bag detection sensor, wherein when the synchronous sensor detects a change from a state in which the bag is absent at the first detection point to a state in which the bag is present at the first detection point, the controller acquires a detection result of the first bag detection sensor regarding the presence or absence of the bag at the second detection point, and when the detection result of the first bag detection sensor indicates that the bag does not exist at the second detection point, the controller recognizes that the bag has an abnormality, and when the synchronous sensor detects a change from a state in which the bag is present at the first detection point to a state in which the bag is absent at the first detection point, the controller acquires a detection result of the second bag detection sensor regarding the presence or absence of the bag at the third detection point, and when the detection result of the second bag detection sensor indicates that the bag does not exist at the third detection point, the controller recognizes that the bag has an abnormality. a synchronous sensor that detects presence or absence of the bag at a first detection point in a transfer path of the bag; a first bag detection sensor that detects presence or absence of the bag at a second detection point in the transfer path, the second detection point being at a same position as the first detection point or on an upstream side of the first detection point in regard to a transfer direction of the bag; a second bag detection sensor that detects presence or absence of the bag at a third detection point in the transfer path, the third detection point being at a same position as the first detection point or on a downstream side of the first detection point in regard to the transfer direction of the bag; and a controller that controls the synchronous sensor, the first bag detection sensor and the second bag detection sensor, wherein when the synchronous sensor detects a change from a state in which the bag is absent at the first detection point to a state in which the bag is present at the first detection point, the controller acquires a detection result of the first bag detection sensor regarding the presence or absence of the bag at the second detection point, and when the detection result of the first bag detection sensor indicates that the bag does not exist at the second detection point, the controller recognizes that the bag has an abnormality, and when the synchronous sensor detects a change from a state in which the bag is present at the first detection point to a state in which the bag is absent at the first detection point, the controller acquires a detection result of the second bag detection sensor regarding the presence or absence of the bag at the third detection point, and when the detection result of the second bag detection sensor indicates that the bag does not exist at the third detection point, the controller recognizes that the bag has an abnormality.