The invention relates to a testing device for checking at least one first medical electrode (1), wherein the testing device comprises at least one first measuring electrode (2), which can be arranged relative to the first medical electrode (1) to be checked in such a way that the at least one first measuring electrode (2) and the first medical electrode (1) to be checked form a first capacitance (C11); a signal generating device (3), by way of which an alternating current voltage can be generated, by means of which the first capacitance (Cn) can be acted upon; an evaluation device (4), which is designed to determine at least one first test result (P11) in relation to the first capacitance (C11) from a measured impedance curve (I) of an impedance caused in response to the first capacitance (C11).