A semiconductor device includes a semiconductor element, a base, and an outer packaging resin. The base has a mounting surface, on which the semiconductor element is mounted, and a groove provided around the semiconductor element on the mounting surface. An outer packaging resin covers the semiconductor element and the base, and is fixed to the base by filling the groove. A bottom of the groove includes a first recess-projection having a first amplitude and a first repetition interval along an extending direction of the groove. The first recess-projection includes a second recess-projection having a second amplitude smaller than the first amplitude and a second repetition interval shorter than the first repetition interval along the extending direction of the groove.