Abstract: It is an object of the present invention to provide: a method for determining endometriosis, in which a blood sample from a subject can be used, and which is capable of determining endometriosis with higher sensitivity and higher precision than those of a conventional method using only a conventional endometriosis marker such as CA125; and a diagnostic kit for carrying out the method of the present invention. The method for determining endometriosis according to the present invention comprises: a step of analyzing an expression of at least one selected from among an anti-syntaxin autoantibody, an anti-PDIK1L autoantibody and an anti-enolase autoantibody; and a step of determining the presence or absence of the onset of endometriosis based on results of said expression analysis.