A medical instrument includes a multilayer wiring board having first, second and third wirings, a fourth wiring formed in a first wiring layer, and a fifth wiring formed in a second wiring layer. A first via conductor electrically connects the third and fifth wirings. A second via conductor electrically connects the fourth and fifth wirings. The medical instrument further includes first and second transistors, a second transistor, and a capacitor mounted on the first wiring layer side of the multilayer wiring board. The drain and source electrodes of the first transistor are electrically connected to the first and second wirings, respectively. The drain electrode of the second transistor is electrically connected to the second wiring. The source electrode of the second transistor is electrically connected to the third wiring. The first and second electrodes of the capacitor are electrically connected to the first and fourth wirings, respectively.
