To make the quality of a failure sure, to take quick measures of failure repair and to improve the operation of a medium handling device by comparing digital expression of an acoustic output of plural sensors with digital expression of a normal output of the sensors and displaying a sensor that emits an abnormal acoustic output.

An output of a data acquisition board 56 that faces an acoustic output of a microphone 38 and an AE sensor 42 is converted into digital expression in a CPU 4. A comparator 54 compares it with digital expression to which the digital expression corresponds and on which an normal acoustic output is stored. When the compared digital expression coincides within the range of an allowable error that is preliminarily defined, it is decided that a failure does not occur. When it does not coincide within the range of the allowable error, it is compared with one or more digital expressions in which abnormal acoustic outputs of the microphone 38 and the sensor 42 are stored. It is decided how and which part fails.