To provide a communication system capable of properly specifying an abnormality position of failure or the like, its abnormality estimation method and an information reading device.

The communication system provided with a plurality of nodes for mutually performing CAN communication through a CAN communication line includes: a memory means for memorizing the detection number of error of the CAN communication by each of the plurality of nodes in every kind of errors; and an abnormality estimation means in which a sum of an accumulation value of the error detection number of bit error stored in the storage means and an accumulation value of the error detection number of form error estimates the maximum node or the CAN communication line connected to the node abnormal.