The present invention discloses an apparatus and a method for diagnosing abnormal conditions, that quantitatively considers acquisition difficulties between abnormal symptoms provided on a computer screen and quantifies acquisition difficulties of the abnormal symptoms through distinctiveness of measuring devices to exactly diagnose the abnormal conditions even under an improved control environment, making it possible for a user to rapidly and easily diagnose the abnormal conditions that may be generated from a complicated device.With the present invention, the abnormal conditions are diagnosed using the sequential diagnosis technique and the Boolean logic between the abnormal symptoms, making it possible to effectively diagnose the abnormal conditions even under masking effects that may be generated between the abnormal symptoms.