An information processing apparatus determines an abnormal unit by: determining whether or not there is an abnormal point in access to a slave unit by a first master unit that controls a plurality of slave units connected by a serial bus; requesting a second master unit having redundancy with the first master unit to access a specific slave unit when the abnormal point is determined to exist in access to the specific slave unit in the determining; and determining a unit having an abnormality by use of an access result relating to the abnormal point determined to have an abnormality in the determining and an access result indicating a result of the request made in the requesting.