Abstract: This invention is composed of detecting means for detecting operating condition of a vehicle, operation data recording device loaded on a vehicle for arithmetic processing detected data to write into external memory unit, and external data processing device (external computer) for processing data stored in external memory unit. And of data detected by the detecting means, numeral value data such as speed, engine r.p.m. or the like are displayed to external display device, and operation or non-operation data are processed arithmetic to data for memorizing at arithmetic processing portion to be written into external memory unit.While, data obtained from other than detecting means are input by external input portion of the operation data recording device to be written into external memory unit.Thus input data and parameter stored in inner memory is enabled to accesse and to debug at any time through connector for maintenance.