1. A log tracing apparatus comprising: processing circuitry: to acquire log data indicating occurrence times of a respective plurality of types of events; to compute a same period probability between the respective types of the events that occurred during a same period, based on the occurrence times indicated by the log data acquired and to compute an association degree between the respective types, using the same period probability; to identify the types corresponding to each other, based on the association degree computed; to make association between the log data of the corresponding types identified and with the occurrence times thereof included in the same period, wherein the processing circuitry acquires first log data on a plurality of types of first events in a first classification and second log data on a plurality of types of second log data in a second classification; wherein the processing circuitry computes the same period probability between each type of the first events and each type of the second events that occurred during the same period, and computes the association degree between each type of the first events and each type of the second events, using the same period probability computed; wherein the processing circuitry identifies the type of second event corresponding to the type of the first event, and wherein the processing circuitry computes the association degree between a certain type d j of the first event and a certain type t i of the second event, using the same period probability between the type d j of the first event and the type t i of the second event and a number of the types of the first events each of which occurred during the same period as the type t i .