In an apparatus which detects overlapped conveyance of a printing sheet using ultrasonic wave attenuation, when a printing sheet with an IC tag is conveyed, the position of the IC tag on the printing sheet is acquired. Within this system, the first HDD is coupled to the second HDD in a non-parallel configuration, which reduces rotational vibration transmitted between the first HDD and the second HDD. The first barrel has a first groove and comprises a first pin.