There is provided an electrode catheter for measuring an electric potential inside a heart of a subject. The electrode catheter includes: a shaft that is inserted into the heart, wherein the shaft includes a distal end portion, and a guide portion that is connected to the distal end portion； a non-contact electrode that is provided on an outer circumferential surface of the distal end portion or the guide portion； and at least one contact electrode that is provided on the outer circumferential surface of the distal end portion and that is configured to make contact with an endocardium of the heart. The non-contact electrode is provided on the outer circumferential surface of the distal end portion or the guide portion so as not to make contact with the endocardium in a state where the contact electrode is in contact with the endocardium.
