Abstract: In the logging device, data at a check point in execution of an application program, a log output condition preliminarily set from outside, and a plurality of log output functions called at each check point are built in the application program; and at normal time, a log output is made only in case that an error level having been specified with a parameter of a log output function is coincident with the normal-time log output condition, and in case that the error level coincident with a trigger level arises, a detailed log at the error level coincident with the abnormal-time log output level is outputted.