A power semiconductor apparatus includes a mold portion, a panel that is conductive and in a flat plate shape, and a plurality of fins. The mold portion includes a power semiconductor element and a base plate that are molded. An opening is formed in the panel into which the base plate is inserted. The plurality of fins is fixed in grooves of the base plate. The panel has a plurality of protrusions on side surfaces forming the opening. Each protrusion has a fifth surface a cross section of which has a shape that tapers down toward an end of the protrusion, the cross section being parallel to a plane extending in the Z direction and a direction in which the protrusion protrudes. The base plate has cover portions covering the fifth surfaces, and is plastically deformed to allow the panel to be fitted in the base plate to fill gaps.