A substrate for a medical device configured to be included in a medical device at least part of which is brought into contact with or inserted into a subject, the substrate for a medical device comprising: a patient circuit that is a circuit on a side of being brought into contact with or inserted into the subject; a ground-side circuit that is a circuit configured to perform at least one of transmission of a signal, reception of a signal, and supply of electric power on the patient circuit and grounded; an insulating layer provided between the patient circuit and the ground-side circuit and providing insulation between the patient circuit and the ground-side circuit; and an isolated circuit provided on the insulating layer apart from the patient circuit and the ground-side circuit on the insulating layer and having a different reference potential from the patient circuit and the ground-side circuit; further comprising a plurality of impedance means (51, 52) for connecting either one of the patient circuit and the ground-side circuit and the isolated circuit, wherein the patient circuit and the ground-side circuit are connected via the isolated circuit and at least part of the plurality of impedance means; wherein: the impedance means is formed of a chip-type electronic component; and the impedance means is located on at least two of a first surface and a second surface that are surfaces in a thickness direction of the substrate for a medical device and an inner layer, and is provided such that at least part of the impedance means overlap along the thickness direction of the substrate for a medical device. a patient circuit that is a circuit on a side of being brought into contact with or inserted into the subject; a ground-side circuit that is a circuit configured to perform at least one of transmission of a signal, reception of a signal, and supply of electric power on the patient circuit and grounded; an insulating layer provided between the patient circuit and the ground-side circuit and providing insulation between the patient circuit and the ground-side circuit; and an isolated circuit provided on the insulating layer apart from the patient circuit and the ground-side circuit on the insulating layer and having a different reference potential from the patient circuit and the ground-side circuit; further comprising a plurality of impedance means (51, 52) for connecting either one of the patient circuit and the ground-side circuit and the isolated circuit, wherein the patient circuit and the ground-side circuit are connected via the isolated circuit and at least part of the plurality of impedance means; wherein: the impedance means is formed of a chip-type electronic component; and the impedance means is located on at least two of a first surface and a second surface that are surfaces in a thickness direction of the substrate for a medical device and an inner layer, and is provided such that at least part of the impedance means overlap along the thickness direction of the substrate for a medical device. the impedance means is formed of a chip-type electronic component; and the impedance means is located on at least two of a first surface and a second surface that are surfaces in a thickness direction of the substrate for a medical device and an inner layer, and is provided such that at least part of the impedance means overlap along the thickness direction of the substrate for a medical device.