Abstract: A highly reliable semiconductor device and power conversion device are obtained. In the semiconductor device, a semiconductor element is mounted on a main surface of a base member. A case includes a side wall surrounding the base member. A support portion is formed on an inner peripheral surface of the side wall on a side of the base member. At least a part of the support portion is in contact with a contact region located inside an outer peripheral end of wiring board on a surface of the wiring board located on the side of the semiconductor element. A sealing member seals the semiconductor element and the wiring board. A terminal member is connected to a region of the wiring board closer to the outer peripheral end than the contact region. The terminal member includes an end portion protruding from a surface of the sealing member.