Provided are a self-diagnosis system and a test circuit determination method that are capable of determining normality of a test circuit which diagnoses a test target circuit. A self-diagnosis system according to an aspect of the present invention includes a test circuit including first and second diagnosis controllers which determine normality of a test target circuit by using an execution result of a test pattern in the test target circuit; and a test circuit determination unit which determines normality of the test circuit by comparing a normality determination result of the test target circuit output from the first diagnosis controller with a normal determination result of the test target circuit output from the second diagnosis controller.