Apparatus and operating method for monitoring micro controller unit having multi-core

Provided is an operating method of a monitoring device configured to monitor a microcontroller unit including a plurality of cores. The operating method includes: transmitting a question message to a first core among the plurality of cores; receiving an answer message from a second core among the plurality of cores; determining whether an operation of the microcontroller unit is abnormal, by using the answer message; receiving answer messages from cores, except for the second core, among the plurality of cores when the operation of the microcontroller unit is abnormal; and detecting an error of each of the plurality of cores by using the received answer messages.