The inter-module communication apparatus comprises: a first module and a second module which operate individually on a processor; a common memory interposed between the first module and the second module for functioning as a communication medium; a plurality of communication paths provided to the common memory for connecting the first module and the second module to be communicable; a transmission unit for transmitting communication data from the first module to the second module; and a reception unit for receiving the communication data transmitted from the first module by the second module. Further, it comprises a processing order relating device for registering a processing order of communication processing, which is set between each communication path constituting a plurality of the communication paths; a processing order relevance register which, for transmission, registers the processing order to the processing order relating device when the processing order is set for the communication data to be transmitted; a reception processing relevance checking device which, for reception, checks with the processing order relating device whether or not there is the processing order set between the communication path which transmitted the received communication data and other communication paths; and a processing order information analyzer which, for reception, analyzes whether or not the received communication data is in compliance with the processing order, when the reception processing relevance checking device confirms that there is the processing order set between the communication path which transmitted the received communication data and other communication paths.