PROBLEM TO BE SOLVED: To provide an electrocardiogram sensor sheet which enables quick and accurate attachment of respective electrodes to prescribed positions.SOLUTION: A base sheet 200 includes a belt-like trunk part AR0 formed continuously in a vertical direction, and a plurality of branches AR1-AR3 branched from the trunk part AR0 in oblique directions and formed. With respect to a peeling direction from the base sheet 200 of a peeling sheet 300, the respective branches AR1-AR3 are formed toward the same direction or toward a direction of crossing it at an acute angle.